Final Report Summary - SOFIA (Enhancement of Cretes potential for a dedicated calibration facility for satellite radar altimeters and for tectonic deformation monitoring using continuously operating geodetic arrays.)
Executive Summary:
The Laboratory of Geodesy and Geomatics Engineering (GeoMatLab) at the Technical University of Crete in Greece is located in Crete, one of the EUs convergence regions, but is a dynamic and developing scientific entity on a European and international scale. Its research activities are on the Global Navigation Satellite Systems, satellite geodesy and deformation monitoring, and on satellite altimetry calibration and validation (Cal/Val).
On the Gavdos island, 40 km south of Crete, the GeoMatLab has established in 2001 and has been operating continuously, as of 2004, a permanent calibration facility for satellite radar altimeters. Four permanent sites exist in the world for providing such absolute calibration of satellite altimeters. Also, GeoMatLab operates a network of continuously functioning GPS reference stations in the western Crete and Gavdos, one of the most active seismic zones in Europe.
Because of its geographical location, GeoMatLab was not able to attract top researchers to boost its scientific excellence and drive it to multi disciplinary research. The infrastructure installed so far needed to be upgraded to keep up with the continuous technological advancement and challenges in altimetry and deformation monitoring. The objectives of this SOFIA project were directed into:
Reinforcing GeoMatLabs research potential through recruitment of senior and junior researchers.
Mobilizing Lab personnel for building its scientific and research capacity;
Developing partnerships with EU research entities with similar scientific interests.
Participating in research projects for scientific advancement and sustainability;
Contributing to regional economic and social sustainable development.
Within the SOFIA Project, modernization and up-scaling of the infrastructure for satellite altimetry calibration and tectonic deformation monitoring have been completed in Gavdos and Crete, Greece. New equipment have been procured and installed at several field sites as well at the central facility in the Laboratory. Recruitment of post-doc researchers resulted in software development to estimate altimeter bias using in-situ and satellite altimeter observations. The applied calibration methodology has been the result of the cooperation with the OCA (France) partnering organization as well as with the other satellite calibrating institute in the USA, i.e. the Jet Propulsion Lab.
In collaboration with the Austrian SRISG partnering organization and ESA as well with CNES (France), a new prototype microwave transponder for calibrating satellite altimeters has been developed and delivered in 2011. This prototype instrument has tremendously enhanced the research capacity of GeoMatLab. Calibration procedures using the transponder are now developed as a result of the collaboration between SRISG and CNES, as well as ESA. Plans are under way for the calibration of the ESA satellites, Cryosat-2 and the upcoming Sentinel-3, as well as the Chinese satellite HY-2 and the French/Indian mission of SARAL/AltiKa using Gavdos and Crete Cal/Val facilities.
As a result of the cooperation with the German partnering organizations (GFZ and DGFI), data from the established GPS sites in Crete and Gavdos are routinely processed using three independent software packages, i.e. GAMIT, GIPSY, and Bernese, for monitoring crustal movements and parameters for the troposphere and ionosphere, but also for determining parameters in the satellite altimeter calibration. Permanent sites for the European EGNOS and the Chinese navigation system of BeiDou/Compass have been established in Crete and enabled GeoMatLab to extend its operations into other international navigation satellite systems.
Collaboration with the SOFIA partnering organizations enabled us to improve the satellite altimetry calibration methodology, as well as the GNSS data processing techniques and efficiency for crustal deformation monitoring.
Project Context and Objectives:
The Laboratory of Geodesy and Geomatics (GeoMatLab) at the Technical University of Crete in Greece is located in Crete, one of the EUs convergence regions, but is a dynamic and developing scientific entity on a European and international scale. The primary focus of its research activities are on the Global Navigation Satellite Systems, on satellite geodesy and crustal deformation monitoring using geodetic data, and on satellite altimetry calibration and validation.
On the small island Gavdos, 40 km south of Crete, the GeoMatLab has established in 2001 and has been operating as of 2004 a permanent calibration facility for satellite radar altimeters. The location of the frontier land of Gavdos constitutes a strategic point for the calibration of satellite altimeters on a world level, and also for monitoring absolute sea level and climate change on a continuous and long-term basis. Four permanent sites exist in the world for providing absolute calibration of satellite altimeters. Three of them are located in Europe (Gavdos in Greece, Corsica in France, Ibiza in Spain is used intermittently), one in the USA (Harvest Oil Platform, California) and one in Australia (Bass Strait, Tasmania).
A competitive advantage of the Gavdos calibration infrastructure is its strategic location in the center of East Mediterranean and some of the special instruments installed at the facility. Dedicated calibration sites, such as Gavdos, which are located on a cross-over point and exactly under their repeating orbits of Jason satellite series, will continue to provide a vital service for modern altimetry missions. If on-site instruments however would not have been upgraded for the future Jason missions and not adjusted to the new challenging measuring techniques, such as the swath altimetry, the Gavdos facility would have been threatened to cease to provide its unique services to the worldwide altimetry community.
Furthermore, the GeoMatLab has been operating a network of continuously functioning Global Navigation Satellite Systems (GNSS) reference stations (CORS) located in the western Crete and Gavdos. Most of these stations are collocated with tide gauges. In addition, the CORS station named TUC2 has been part of the European Reference Frame Permanent network (EPN) as of June 2004 and was officially the first such EPN station in Greece.
Algorithms and software have developed by GeoMatLab for controlling and monitoring the quality of the satellite geodetic data, as well as for monitoring crustal deformation in Crete, which is one of the most active seismic zones in Europe. This has been performed with the use of dedicated GNSS arrays.
Participation of GeoMatLab in scientific organizations such as the European EUREF permanent network, the Ocean Surface Topography Science Working Team of the Jason satellite mission, the Calibration Validation Research Team of ESA, as well as the collaboration with European and international experts revealed that despite the strengths of the GeoMatLab, there were specific activities that should have been performed to enhance its scientific potential and operational capabilities for satellite altimetry calibration and deformation monitoring. Because of its geographical location in one of the EUs convergence regions, GeoMatLab was not able to attract top researchers to boost its scientific excellence and drive it to multi disciplinary research. The infrastructure installed so far needed to be upgraded to keep up with the continuous technological advancement and challenges in altimetry and deformation monitoring. The GeoMatLab was unable to purchase or develop prototype instruments (such as the transponder) by its own resources to meet the growing needs of future altimeters. Participation and funding from European programs was a necessity to ensure continuous operation of this important site located in a less advanced region of the EU.
Along these lines, the objectives of SOFIA project were as follows:
(1) The first objective aimed at developing strategic partnerships with well established European research entities and in particular: (a) the Observatoire de la Cote d'Azur (OCA), France, which has been running the Corsica Cal/Val site with knowledgeable and experienced research teams and the support of the French Space Agency (CNES: Centre National dEtudes Spatiales); (b) the Space Research Institute of the Austrian Academy of Sciences which has experience in calibrating altimeters using dedicated microwave transponders. Thus, the know-how existing in the Space Research Institute for transponder data analysis would be transferred to the less advanced region of Crete; (c) the Deutsches Geodätisches Forschungsinstitut (DGFI) in Munich, Germany to exchange know-how and experiences for automating the monitoring of crustal deformation of West Crete using the existing GNSS arrays; and the GeoForschungsZentrum(GFZ) in Potsdam, Germany for the exchange of experiences for replacing expensive radiometric measurements with dedicated instruments at Gavdos Cal/Val site with the GNSS zenith troposphere delays.
(2) The second objective was to enhance the Gavdos Cal/Val present capabilities by developing new calibrating instruments and procedures, so that GeoMatLab was prepared for the calibration of future altimeters, such as the European Cryosat-2 and Sentinel-3, through a collaboration with the European Space Agency;
(3) The third objective was to reinforce its research potential by recruiting at least two new researchers: one to carry out research on geodetic signal monitoring methodology and software development and another to enhance satellite altimetry calibration procedures and instruments;
(4) The fourth objective was to perform dissemination and promotional activities to increase GeoMatLabs visibility. This had to be done with the organization of two outreach workshops: one international on satellite altimetry calibration and deformation monitoring with invited international experts and stakeholders, and another regional to inform local and regional authorities on the ways that Structural Funds could be used to exploit GeoMatLab research results for regional social and economic development.
Within the SOFIA Project, modernization and up-scaling of the infrastructure for satellite altimetry calibration and tectonic deformation monitoring have been completed in Gavdos and Crete, Greece. New equipment have been procured and installed at several field sites as well at the central facility in the Laboratory. Recruitment of post-doc researchers resulted in software development to estimate altimeter bias using in-situ and satellite altimeter observations. The applied calibration methodology has been the result of the cooperation with the OCA (France) partnering organization as well as with the other satellite calibrating institute in the USA, i.e. the Jet Propulsion Lab.
In collaboration with the Austrian SRISG partnering organization and ESA as well with CNES (France), a new prototype microwave transponder for calibrating satellite altimeters has been developed and delivered in 2011. This prototype instrument has tremendously enhanced the research capacity of GeoMatLab. Calibration procedures using the transponder are now developed as a result of the collaboration between SRISG and CNES, as well as ESA. Plans are under way for the calibration of the ESA satellites, Cryosat-2 and the upcoming Sentinel-3, as well as the Chinese satellite HY-2 and the French/Indian mission of SARAL/AltiKa using Gavdos and Crete Cal/Val facilities.
As a result of the cooperation with the German partnering organizations (GFZ and DGFI), data from the established GPS sites in Crete and Gavdos are routinely processed using three independent software packages, i.e. GAMIT, GIPSY, and Bernese, for monitoring crustal movements as well as parameters for the troposphere and ionosphere, but also for determining parameters in the satellite altimeter calibration. Permanent sites for the European EGNOS and the Chinese navigation system of BeiDou/Compass have been established in Crete and enabled GeoMatLab to extend its operations into other international navigation satellite systems. Collaboration with the SOFIA partnering organizations enabled us to improve the satellite altimetry calibration methodology, as well as the GNSS data processing techniques and efficiency for crustal deformation monitoring.
The scientific results obtained so far within the SOFIA project, have been presented at several international workshops and conferences, such as the Ocean Surface Topography Science Team meeting, the ESA Cryosat and ICESAT meeting, the SPIE Conference, the ESAs Living Planet Symposium, the Week of Innovative Regions 2010, etc. Six scientific papers have been published in the Marine Geodesy and the Advances of Space Research journals. In addition, the GeoMatLab personnel attended short training events in GNSS data processing (organized by INGV, Italy), in satellite altimetry and GIPSY software for precise point positioning (organized by JPL, USA) and in satellite radar interferometry (organized by Terrafirma, Italy). Participation in summer schools organized by the International Association of Geodesy and the European Space Agency also increased GeoMatLabs visibility and improved its research capacity. Involvement in international research teams as principal investigators (i.e. the Cryosat-2 and SARAL/AltiKa calibration-validation research teams) enhanced the Labs visibility and offered the possibility for participating in forthcoming research projects.
Strategic collaborations with national (i.e. the Greek Cadastral, Leica Company, etc) to jointly make use of the GNSS arrays throughout the country and involving the network developed in the SOFIA project, as well international Partners have been established. Besides the International Conference, Meetings for the visibility of the GeoMatLab, strategic partnerships of GeoMatLab with international Organizations have emerged, such as the Indian Space Research Organization, European Space Agency, French CNES Space Agency, the Chinese First Institute of Oceanography and the Chinese GNSS Research Center, Wuhan University, China.
After the completion of this Project, the methodology and facilities at the Gavdos and Crete for the calibration of satellite altimeters have improved and were made capable to be extended for other international altimetric satellites using alternative and independent techniques, but also newly developed instruments. Collaboration with all partnering organizations that took place during this reporting period have resulted in long-term associations by signing 3 Memorandum of Understandings with the Austrian, German and French Partnering Institutes.
GeoMatLab has built and established its caliber and capacity within the international community and research teams for satellite calibration and deformation monitoring. It also enhanced its research potential and visibility. The dedicated Gavdos and Crete Cal/Val facilities have established as one of the four international satellite calibration sites in the world.
The established dedicated Cal/Val site is now fully instrumented to provide an independent (in-situ) determination of sea-surface observations and provide the basis for calibrating the altimetric measurements made by the satellites as they overfly the location. It will provide fundamental calibration information in the centre of the East Mediterranean for an uninterrupted monitoring of the Jason satellite and its successors, as well as the European Cryosat-2, and Sentinel-3 and Chinese and French/Indian missions. Also, the established permanent GNSS network in west Crete and Gavdos is able to monitor crustal deformation in one of the most seismic active regions in Europe on a continuous basis and provide valuable information for earthquake research and interpretation. This site has become essential infrastructure in monitoring sea level variations and climate changes for our planet.
Project Results:
Description of the main S&T results/foregrounds (max length 25 pages)
The work performed during the SOFIA project led to the accomplishment of all foreseen project objectives. The GeoMatLabs international visibility has been significantly enhanced leading to the establishment of strategic partnerships with European (i.e. SOFIA Partnering Organizations, European Space Agency, CNES (French Space Agency), Danish Technical University, Danish Space Center) and international Institutes (i.e. Indian Space Research Organization, First Institute of Oceanography-China, Chinese Global Navigation Satellite Systems Center-Wuhan University, China). The research capacity of GeoMatLab has been built up by its research staff and the established infrastructure is capable and ready for cutting-edge research on satellite altimetry calibration and ground deformation monitoring. The Laboratory now possesses a research infrastructure that is unique not only in regional/national but also at international level. To this end, the established scientific excellence of the GeoMatLab research team in conjunction with the developed infrastructure led to overcome its disadvantage of being located in a convergence European region and achieve results that match those performed at research institutes located in more advanced countries.
The scientific and technological results accomplished during the 42 months of this Project duration can be grouped into: a) infrastructure modernization and up-scaling, and b) research capacity enhancement. These S&T results have been properly disseminated into public and private entities and stakeholders (a description is given in the next Section) and their exploitation is expected to secure funding of the GeoMatLab activities for the upcoming years.
The following Sections describe in detail the scientific and technological results of the SOFIA project, as well as the activities performed that allowed the establishment of strategic partnerships.
1. Infrastructure modernization and up-scaling
The developed infrastructure has been distributed at several sites over Gavdos and west Crete, Greece. The Operations Control Centre is located in the TUCs campus and has been developed for fast and efficient processing, as well as for data archival, and for controlling the field units. Next to the Operations Control Center also exists a permanent and continuously operating Global Positioning System (GPS) station, named TUC2, operating as of 2003. This station is part of the European Permanent Network for EUREF. A new EGNOS station, coined TUC3, has been installed in the University Campus and is the first EGNOS site in Greece. TUC3 is collocated with a BeiDou/Compass chinese satellite station (TUC4). BeiDou is the Chinese navigation system and this TUC4 site is the first one to be installed in Europe. Collaboration with the Chinese GNSS Research Center, Wuhan University, China, made this installation possible. GeoMatLab personnel are currently trained by Chinese researchers in processing BeiDou satellite data with the PANDA software.
The main satellite calibration facility is located at Gavdos island; on land property, bought by the University for the needs of satellite calibration. The Gavdos calibration facility includes the Karave (tide gauges, meteo sensors, GPS, etc.) on the harbour, the Theophilos (central communication site and control) and the DIAS sites (transponder). The RDK1 site on the south Crete is considered to be a secondary Cal/Val site, because it has been installed along the north part of the ground track of the Jason satellites. In south west Crete, the Chrysoskalitissa site (CRS1) has been upgraded and is currently a fully-equipped Cal/Val site (GNSS receiver, main and back-up tide gauge, meteorological sensors, etc.) ready to be used for the calibration of the Jason series and the Chinese HY-2 satellite altimeter.
The deformation monitoring network in west Crete has been also enhanced through the establishment of the SUG1 GNSS site in south west Crete. This SUG1 site, as well as the previously established sites at Petra Seli and Menies (SEL1 and MEN2, respectively) concluded the GNSS network for monitoring any velocity transient effects and other phenomena of the earths crust at the subduction zone in Crete. All these GNSS sites have been upgraded with the state-of-the-art, reliable, and accurate scientific instrumentation.
The basic equipment and software that has been purchased, installed and operarate during the SOFIA project is as follows:
Three GNSS receivers. The first one is a receiver capable to lock data from the European Geostationary Navigation Overlay System (EGNOS) and the other two are state-of-the-art units that replaced the old ones operated for several years. More specifically the EGNOS receiver has been installed inside TUC campus in a remote area dedicated for the development of the first EGNOS Data Collection Station in Greece. One of the new receivers replaced the old one operated at the TUC2 site (now transferred and installed at the Rodakino site in south Crete) while the second one (GVD8) replaced the one operated at the Gavdos Karave site (GVD5);
Six tide gauges. Four of them have been installed at the main satellite calibration location in Gavdos, i.e. Karave site, while the other two have been set-up at the Chrysoskalitissa site in southwest Crete. More specifically, at the Karave site a pressure tide gauge (KVR5), an acoustic tide gauge (KVR4) and a radar tide gauge (KVR6) have been installed and are fully operational. The later tide gauge (KVR6) has been setup inside the Karave concrete shack in the Gavdos harbor, where inside it there exists a well for reliable sea level measurements. This installation has been carried out to have a protected sea level measuring system that will not be influenced by weather conditions, and thus it will provide reliable measurements for the sea surface height. On-site calibration of the sea-level measurements obtained by these tide gauges will be made by a staff gauge also installed there at the harbor. In south west Crete, the Chrysoskalitissa Cal/Val facility has been equipped with one pressure (SVR1) and one radar tide gauge (SVR2). This site will be used for the calibration of the Chinese HY-2 satellite altimeter and is expected to play a dominant role in future GeoMatLabs scientific and research activities. It will be the first time that this Chinese satellite altimeter will be calibrated by a European institute and outside China;
Three meteorological sensors. For the Chrysoskalitissa and Gavdos Karave sites meteorological sensors, directly connected directly to GNSS receivers (thus ensuring data transfer through GNSS raw data), have been purchased and installed. Additionally, the old meteorological sensors installed at the Gavdos Theophilos site have been re-calibrated in the Lab and replaced, when damaged;
One choke ring GNSS antenna. This has been installed at the Chrysoskalitissa CRS1 GNSS site in GeoMatLabs effort to improve precise geodetic positing at this site to meet the satellite altimeter calibration standards;
One prototype instrument for monitoring ionospheric scintillations;
Software for GNSS data processing. GeoMatLab is now performing GNSS data processing using different software. The newly acquired software (BERNESE) can produce Total Electron Content estimates for the ionosphere.
Batteries for operation of the GPS buoys, used for measurement of the sea surface height simultaneously when the Jason-2 satellite was flying over the boat at sea. These buoys are property of the Hellenic Centre for Marine Research but were lend to the Lab for the purpose of this Project.
Modems, cables and other peripherals for the communication links. Currently there are two satellite links (at Gavdos Theophilos and Chrysoskalitissa sites) and two mobile telephone GPRS connections (at Gavdos Karave and Rodakino sites).
One file-server main computer. This computer has been placed in a protected environment at the major TUCs Data Center on Campus, and is used for data archival, data base operation, data processing, etc;
Two personal computers and notebooks with their peripherals. These computers were by the Project Secretariat and the recruited post-doc researchers, while the notebooks have been used in the field for in-situ data downloading.
Software upgrade for remote, automated GNSS data management;
Solar panels and accessories for power supply at the MEN1 GNSS site as well as the EGNOS site;
Replacement of the batteries used for power supply of the Gavdos main facility;
The current state of the GeoMatLabs infrastructure is presented in the following Sections.
1.1. TUC Campus Facilities
The instrumentation installed at TUC Campus facilities are:
A Leica GNSS 1200+ receiver (named TUC2) along with a Vaisala PTU 200 meteorological station.
A PolaRx3eGPRO EGNOS/GPS station (called TUC3).
A UNICORE UB240 CORS Compass/GPS station (called TUC4).
The TUC2 station is installed inside a concrete shack close to the GeoMatLab's facilities. TUC2 is part of the European Reference Frame (EUREF) regional GNSS network since 2004. Its data are available on line in the internet as part of the permanent European GNSS net (http://www.epncb.oma.be/_trackingnetwork/siteinfo4onestation.php?station=TUC2). TUC2 station provides to EUREF hourly and daily GPS (American) and Glonass (Russian) data as well as meteorological measurements. Users can access data through the EUREF ftp servers (ftp://igs.bkg.bund.de/EUREF/obs/2010).
The TUC3 is installed inside a different concrete shack close to the Laboratory's facilities on Campus. TUC3 station is operated as a permanent GNSS station and therefore must follow the IGS (International GNSS Service) standards for CORS (Continuously Operating Reference Stations). This is also part of the EGNOS (European Geostationary Navigation Overlay Service) data collection network.
TUC4 station is the first European GPS/Compass GNSS station (Compass/BeiDou is the Chinese satellite navigation system). The receiver is temporarily installed on the roof of the Laboratory building for training and easy access.
A Meteorological sensor (Vaisala PTU200) is directly connected to the TUC2 GNSS receiver using a serial cable. In this way, the GNSS receiver acts as a data logger for the meteorological sensor. Measurements are stored in the widely used meteorological RINEX format inside the satellite receiver. The GNSS receiver is accessed using a TCP/IP interface (The university LAN network is accessible inside the concrete shack).
1.2. Gavdos Cal/Val facility
The following instruments have been installed at the Gavdos Cal/Val facility within the framework of the SOFIA project:
Karave site at the Gavdos harbor
The Karave site in Gavdos is the main site used for satellite altimeter calibration at the harbor. The instruments installed there are:
A Leica GNSS receiver, called GVD7A Paroscientific MET4 meteorological sensor, attached to the GVD7 receiver;
A back-up Leica GNSS receiver (GVD8). This state-of-the-art receiver measures the American GPS and the Russian Glonass signals as well;
An OTT Kalesto radar tide gauge (KVR3)
A General Acoustics LogALevel backup tide gauge (KVR4)
A Valeport tide master pressure tide gauge (KVR5);
A Vega radar tide gauge (KVR6);
A staff gauge for onsite calibration of the sea-level measurements made by all Karave tide gauges in the Gavdos harbor;
A LINUX downloading heavy-duty computer.
A GPRS communication link.
All sensor measurements (except KVR3) are downloaded daily and archived at the Thales main file-server computer in the University Campus in Chania.
Theophilos central site in Gavdos
The Theophilos site in Gavdos is the main satellite calibration infrastructure on Gavdos Island. All instruments placed there are located at a 4,000 m2 plot owned by the Technical University of Crete. Originally when there was only a poor UHF data connection to the island, all data transmissions where tunneled through Theophilos site at the Gavdos harbour and then to the University facilities in Crete.
The instruments installed are:
A Leica RS500 GPS Receiver along with a Leica AT504 GPS choke ring antenna comprise the GVD0 GNSS site;
An Aanderaa Automatic weather station has been calibrated in the Lab and replaced;
A DORIS Satellite beacon along with a Vaisala PTU200 meteorological station. (Owned and operated by CNES, France)
An industrial computer as well as the other sensors installed at this Gavdos Central facility;
Dias transponder site
The DIAS site in Gavdos is located under the crossover of Jason satellite Passes No 018 & 109. The old microwave transponder (property of the Austrian Partnering Organization) has been installed there since 2003. Under the framework of the SOFIA project, several GPS and geodetic leveling surveying have been conducted for a) determination of the transponders absolute ellipsoidal height, and b) estimation of the atmospheric delay parameters (wet troposphere and ionosphere) for correcting Jason-2 satellite altimeter measurements. The transponder has been disassembled and shipped from Gavdos to CNES French Space Agency in Toulouse for examination, calibration, and upgrading in June 2012. The site is to be occupied by the newly developed TUC transponder for the calibration of Jason satellites.
1.3. Rodakino Cal/Val facility: RDK1
The Rodakino Cal/Val facility is at the south central coast of Crete and under the ground track of the Jasons Pass 109. This facility serves as a back-up satellite calibration site and has been used to verify the altimeter bias results obtained by the Gavdos Cal/Val facility for the determination of the Jason-2 satellite.
A radar tide gauge station (RDK1, type: Vegapuls-61) with its accompanying data logger (Vegamet-624) and a Leica (Smart 6200) GPS receiver had been initially installed at Rodakino site on 6 March 2009. The GNSS receiver was then replaced with a Leica GRX1200GG PRO receiver and a Leica AT504 choke-ring antenna to enhance the sites performance. Data are transferred to the Operations Control Center in the University Campus via GPRS communications link.
1.4. Chrysoskalitissa Cal/Val facility: CRS1
A Leica GRX1200GG PRO GNSS receiver along with a Leica AX1202 GG antenna has been operating at Chrysoskalitissa site since 8 March, 2008. A Vaisala PTU300 meteorological sensor was installed on March 5 2010. A pressure tide gauge station (Valeport Tidemaster) has been installed on April 25 2012 (SVR1). An OTT RLS radar tide gauge was installed at Chrysoskalitissa site on June 2012 (SVR2). Data from this field measuring units are transferred via a satellite communication link to the Operations Control Center at GeoMatLab.
The Crysoskalitissa site will serve as the main calibration facility of the Chinese HY-2 satellite altimeter.
1.5. Other GPS sites for crustal deformation monitoring
GeoMatLab has installed three GPS sites in collaboration with the North Carolina State University, USA, along the direction of the North-South axis in Crete. These sites are equipped with Trimble NetRS GPS receivers and Trimble Zephyr Geodetic GPS antennas. Menies (MEN1) site was installed on 20 November, 2009 but was vandalized on 27 December, 2009. A new installation and a safer location has been chosen close and the station has been re-installed (MEN2). The Seli (SEL1) site in the central west Crete was installed on 10 July, 2009. The Sougia (SUG1) site in the south west Crete was installed on 5 November, 2010. The Technical University of Crete and the North Carolina State University, USA have signed a Memorandum of Understanding for scientific collaboration that led to the installation of three GPS receivers at the North-South axis of western Crete.
In order to be able to install and maintain these instruments at these remote field locations, several field trips have been carried out. For each field trip, a Traveling Report has been written and submitted. Moreover, details regarding the technical characteristics, operational capabilities, data storage and archival of the GeoMatLab instrumentation are provided in DL2.1 and its respective Annexes. This Section presented in detail the work conducted during the reporting period in terms of instrument maintenance, infrastructure upgrading, etc. All this work has been conducted under the framework of SOFIA project WorkPackage 2, Task 2.1.
1.6. Development of a prototype microwave transponder
The infrastructure presented in Sections 1.1-1.5 is considered to be the conventional equipment for the establishment of satellite altimetry calibration facilities and GNSS network for crustal deformation monitoring. During the SOFIA project, GeoMatLab was able to deliver a prototype microwave transponder to serve as an alternative and independent technique for calibration of satellite altimeters.
Microwave transponders have been proposed as an alternative tool for satellite altimetry calibration more than 10 years now. However, in the world, only few transponders have been built and implemented for this reason. In Europe there are only two active transponders: one is located in European Space Agency Observatory in Svalbard, Norway (more than 20 years old, mainly used for the Cryosat-2 calibration) and another old transponder in the Gavdos Cal/Val facility (more than 15 years old, property of the Austrian Partnering Organization). A microwave transponder is considered to be a stable and sharp calibrating target on the ground when the satellite flies over it, but it acts as if it were on the sea, yet with known properties. It receives, amplifies and retransmits, with minimal distortion, a satellite radar altimeter signal, which in turn is recorded on-board the satellite. The two-way travel time of the signal, after corrections for the atmosphere delays and tides, yields the range between satellite and transponder. This transponder can thus be used to calibrate the range measured by the satellite to the earth, the signal delays in the atmosphere and the effective cross section (sigma-naught) of the reflection in nadir-looking altimetry.
Under the framework of the SOFIA project, a prototype transponder has been constructed mainly for the calibration of the European Cryosat-2 and Sentinel-3 altimetric missions. As mentioned before the operation of a transponder relies on the reception by the satellite of an amplified signal produced by the transponder on land. However, satellite altimeters have specific thresholds in the signals power reception capability. If the satellite receives a signal above certain thresholds then it will be destroyed its sensors and possibly causing a damage of several million euros to the operational agency; in our case the European Space Agency. For this reason the specifications as well as the construction phases of the new ptototype transponder were set, specified, examined, and monitored by the responsible personnel (managers and technicians) for Cryosat-2 and Sentinel-3 missions in the European Space Agency.
The technical specifications of this new prototype instrument have been defined through joint efforts of GeoMatLab, ESA, CNES and the Austrian Partnering Organization. An invitation to tenders for the instrument manufacture had been then published in August 2009.
PRISMA Electronics SA is the industrial company, awarded the construction of the new transponder. Regular exchange of emails and teleconferencing between PRISMA, GeoMatLab and ESA, have been performed for continuous monitoring and review of the transponder manufacturing progress and to define technical details, not given at the initial technical specifications documents. Besides this communication exchange, meetings with ESA personnel in the Netherlands also took place.
A meeting at the European Science and Technology Center, ESA in Noordwijk, the Netherlands, took place on 26th August 2010 with representatives from ESA, PRISMA and GeoMatLab. The main purpose of this meeting was to monitor and review the progress on the transponder design/test/performance, but also cover some aspects about the location and the setting around the proposed calibration site in Crete.
The transponder has been delivered to TUC on 10 November 2010, however testing of its operational capabilities into simulated or real life conditions had to be conducted. There was a significant delay for the implementation of these tests, mainly due to the need for including some extra electronics parts and monitoring sensors inside the transponder. Moreover, there was a continuous inspection on the optimum transponder assembly, regarding the orientation of the transponders antennas and the way they were supposed to be placed outside the transponder itself. After a series of modifications and adjustments, the final transponder assembly with the mounted antennas has been agreed upon by ESA and finally manufactured by PRISMA private company.
Calibration and validation of the transponder itself, under simulated in-house conditions has been conducted at ESTEC/ESA specialized chambers in Noordwijk, the Netherlands. These specialized, in-house tests have been performed from March to June 2012. A meeting in ESA was arranged on March 2012 to evaluate the performance and review the newly developed prototype microwave transponder. The meeting took place in the ESA premises in Noordwijk, the Netherlands on Thursday 8-March-2012 and Friday 9-March-2012. In the meeting, a science team from ESA (Dr. Mavrokordatos, Dr. Borde and Dr. Rolo), a delicate of the manufacturing company, Prisma Electronics (Mr. Komninos) and the SOFIA Project Coordinator participated. During the tests conducted in ESTEC in the Netherlands, several problems have been encountered and resolved by ESA personnel. Finally, the transponder has successfully passed all calibration and verification tests and delivered to GeoMatLab in Crete in June 2012. Thus, Task 2.2 of the SOFIA project has been successfully accomplished.
2. Enhancement of GeoMatLabs research capacity
Section 1 presented the modernization and up-scaling of GeoMatLabs infrastructure as well as the construction of a prototype transponder instrument for satellite altimeter calibration. The existence of high-tech instruments is a precondition for the performance of cutting-edge research especially in engineering disciplines like satellite altimetry, satellite navigation systems and deformation monitoring. However, this is not enough and the researchers assigned to perform this Project research had to be well qualified. A main disadvantage of GeoMatLab is the difficulty to recruit experienced researchers because of its location at a convergence European region and the fact that the financial resources available are far less than in other more advanced countries.
To this end, GeoMatLab used the resources available from the SOFIA project to a) recruit three experienced researchers, and b) to build up the research capacity of existing team members. The latter was successfully performed through the exchange of know-how with the, the Indian Space Research Organization, The Jet Propulsion Laboratory, in the USA, the Chinese Research GNSS Center in Wuhan, The First Institute of Oceanography in Quigdao, China and certainly with the SOFIA partnering organizations, as well as the participation of GeoMatLab personnel in international conferences, workshops and training events. The following Sections will present the main results obtained during the SOFIA project lifetime in terms of improvement of GeoMatLabs research capacity.
2.1. Recruitment of experienced researchers
Three experienced (post-doc level) researchers have been recruited under the framework of the SOFIA project: two to enhance satellite altimetry calibration procedures and instruments and another to carry out research signal deformation monitoring methodology and software development.
One of the main activities in the GeoMatLab group is the calibration/validation of altimetry satellites. Such a work requires the development of algorithms that are using the data from the altimetry satellites, the data processing of GPS and the easy access and processing of data coming from on-site sensors, such as tide gauges. GeoMatLab installed a number of GPS stations and tide gauges in the Gavdos and south Crete areas which provided the required data to validate and expand the work on the satellite altimetry calibration and validation.
During the SOFIA project, improvement of existing and development of new algorithms in the satellite altimetry calibration/validation as well as the design and development of a software suite (called TUCaliBrit) were the main achievements regarding satellite altimetry calibration. This software uses data from the instruments installed at Gavdos facility (tide gauges, GPS receivers, meteorological sensors, etc.), apply several models (i.e. the marine geoid models, Mean Sea Surface, regression, filtering and prediction models) as well as the results from the GPS processing to determine the altimeter bias and corrections for other parameters of satellites flown over Gavdos. Currently, the user of TUCaliBrit has the possibility: i) to select among various marine geoid, mean sea surface and mean dynamic topography models, ii) to initialize the newly developed wet tropospheric model for coastal regions, as provided by Shannon Brown et al., and iii) to statistically analyze the extracted calibration results in order to choose the appropriate procedures and models that best fit the Gavdos Cal/Val local conditions.
The results obtained by the calibration methodology employed in Gavdos Cal/Val facility have been presented at relevant workshops (e.g. Ocean Surface Topography Science Team, Coastal Altimetry Workshops, etc.) as well as in scientific journals (i.e. Marine Geodesy, Advances in Space Research). The Gavdos Cal/Val facility has a proven record for reliable estimates of bias values in the satellite altimeters, which are in accordance with the values reported by the other three international calibration sites in the USA, France, and Australia.
Besides the conventional sea-surface calibration methodology, GeoMatLab also developed, in collaboration with ESA, CNES and the Austrian Partnering Organisation, a software suite for the determination of the Jason-2 satellite employing the existing Gavdos transponder. This software will serve as the main processing tool to analyze the data obtained by the newly developed prototype transponder.
Furthermore, through the collaboration with other Greek (i.e. Aristotle University of Thessaloniki, University of Aegean) and European (i.e. Danish Technical University) institutes the development of local geoid and mean sea surface models, to be applicable in Gavdos, was realized. These local reference models tend to reveal possible correlations between satellite altimetry data and sea floor bathymetry at the centimetre level. Also, the use of altimetric measurements for monitoring ionospheric disturbances caused by tectonic motion is under investigation at the subduction zone. This work is expected to be finalized in 2013 ans is not part of the SOFIA objectives.
Monitoring of tectonic motion present in the area of Crete was one of the main objectives of the second post doc researcher. To accomplish this Task the first step was to perform accurate, precise and reliable analysis of the GPS data obtained by the TUC-net GNSS network. During this reporting period this was feasible through the processing of geodetic data using 3 different scientific software (i.e. GAMIT, Bernese, GIPSY) that allow accurate determination of each station coordinates and the respective 3-dimensional rate of their movement.
Time series analysis of the data obtained by the GNSS array in Crete made feasible to identify long-range, power-law correlation in these geodetic data. Abrupt change detection algorithms for the identification of weak signals (possibly related to silent earthquakes) have been also developed and implemented in GeoMatLabs TUC-net geodetic data.
2.2. Exchange of know-how with partnering organisations
The SOFIA partnering organisation were: the Austrian Academy of Sciences (SRISG), Austria, the Observatoire de la Cote d Azur (OCA), France, the Deutsches Geodatiches Forschungsinsitut (DGFI), Germany and the GeoForschungsZentrum Potsdam (GFZ), Germany. The exchange of know-how with these well-established European entities was performed through dedicated visits, exchange of emails and teleconferences, meetings and organization of international conferences/workshops.
The main result of the collaboration between GeoMatLab and SRISG has been the development of the software to determine the Jason-2 altimetric bias using the SRISGs Gavdos transponder. This is an important asset in GeoMatLabs research capacity s that the developed technical skills are now to be used to exploit its newly developed, prototype transponder for the Jason-2 altimeter. Moroever, SRISG assisted significantly GeoMatLab to define the technical specifications for the newly developed transponder.
The collaboration between GeoMatLab and OCA-France focused on the conventional sea-surface calibration methodology. Advances on processing algorithms, models and statistical analysis of retrieved data were possible through this collaboration. Also, dedicated boat field campaigns for the determination of the instantaneous sea surface height as well as the geoid undulations slope at the Gavdos area have been conducted following recommendations provided by the OCA Partnering Organisation that has long-term experience in the performance of similar field campaigns.
The German Partnering Organisations assisted GeoMatLab to build up its research capacity in terms of GNSS data processing and crustal deformation monitoring. More specifically, the methodology to determine the wet troposphere and the ionosphere delay using the TUC-net GNSS array has been developed. These products are essential input in both calibration methodologies (sea surface and transponder calibration) employed by the GeoMatLab team. Processing of geodetic data using the Bernese software was feasible after specialised training events conducted by the German Partnering Organisations. Currently, geodetic data are processed by GeoMatLab employing three scientific software (i.e. GAMIT, Bernese and GIPSY) to provide reliable estimation of the coordinates and velocities of the TUC network in West Crete and Gavdos sites as well as the production of continuous time series of geodetic positioning solutions. These products are fundamental inputs for crustal deformation monitoring and abrupt change detection research.
Section 2 presented the work performed during the SOFIA project to enhance GeoMatLabs research capacity. A proof of this statement is corroborated by the GeoMatLabs publications record during the Project. During this 42 month of the SOFIA project, GeoMatLabs Project work was published in 13 peer-reviewed articles in scientific journals and workshop proceedings. In addition, 17 presentations (oral and poster) have been given at international conferences and workshops all over the world.
Summing Up
The main objective of this SOFIA project has been to improve the research capacities of GeoMatLab. This was performed through (1) the modernization of the infrastructure, (2) the development of a new prototype transponder instrument for satellite altimeter calibration, (3) the exchange of know-how with the partnering organizations, (4) recruitment of senior and junior researchers, (5) increase its participation in European research projects and international scientific teams, and (6) enhancement the transition from research to regional social and economic sustainable development.
After the completion of this Project, the methodology and facilities at the Gavdos and Crete for the calibration of satellite altimeters have improved and were made capable to be extended for other international altimetric satellites using alternative and independent techniques, but also newly developed instruments. Collaboration with all partnering organizations that took place during this reporting period have resulted in long-term associations by signing 3 Memorandum of Understandings with the Austrian, German and French Partnering Institutes.
GeoMatLab has built and established its caliber and capacity within the international community and research teams for satellite calibration and deformation monitoring. It also enhanced its research potential and visibility. The dedicated Gavdos and Crete Cal/Val facilities have established as one of the four international satellite calibration sites in the world. Such stature is earmarked by including the Gavdos Cal/Val facility in the presentation, for the dedicated Cal/Val sites in the world, to be given at the 20 years of progress in Radar Altimetry Symposium, in Venice, Italy, 24-29 September, 2012. The established dedicated Cal/Val site is now fully instrumented to provide an independent (in-situ) determination of sea-surface observations and provide the basis for calibrating the altimetric measurements made by the satellites as they overfly the location. It will provide fundamental calibration information in the centre of the East Mediterranean for an uninterrupted monitoring of the Jason satellite and its successors, as well as the European Cryosat-2, and Sentinel-3 and Chinese and French/Indian missions. Also, the established permanent GNSS network in west Crete and Gavdos is able to monitor crustal deformation in one of the most seismic active regions in Europe on a continuous basis and provide valuable information for earthquake research and interpretation. This site has become essential infrastructure in monitoring sea level variations and climate changes for our planet.
Negotiations with the satellite operators, such as ESA, are under way for funding the establishment of a permanent calibration site for Sentinel-3 in the south west of Crete using the developed transponder. A site with a triple cross over of the Jason, Sentinel-3A & 3B and AltiKa satellites over west Crete has already been identified, tested, and selected. In the same token, a permanent site at CRS1 in southwest Crete is planned for the calibration of the Chinese satellite altimeter.
The Project has also contributed to regional development by unveiling a problem in land subsidence of 2cm/year caused by excessive pumping of groundwater for irrigation in East Crete and by discovering a power-law, and long-range correlation in the observed deformation signals of two GNSS sites. This may have an impact on earthquake research for the region. Finally, local engineers are also using the precise positioning data provided by the established west Crete network of permanent GNSS sites to improve their accuracy and operations cost.
Potential Impact:
Potential impact, main dissemination activities and the exploitation of results (max 10 pages)
1. Potential Impact
Coastal zones in Europe contain large human populations and significant socio-economic activities. They also support diverse ecosystems that provide important habitats and sources of food. One-third of the European Union population is estimated to live within 50 km of the coast, and some 140 000 km2 of land is currently within 1-m of sea level. Significantly inhabited coastal areas in countries such as the Netherlands, England, Denmark, Germany and Italy are already below normal high-tide levels, and more extensive areas are prone to flooding from storm surges. Climate change is an additional pressure and is likely to have significant impacts on coastal zones, particularly via sea-level rise and changes in the frequency and/or intensity of extreme weather events, such as storms and associated surges.
Direct impacts from sea-level rise include inundation and displacement of wetlands and lowlands, coastal erosion, increased storm flooding and damage, increased salinity in estuaries and coastal aquifers, and rising coastal water tables and impeded drainage. Potential indirect impacts include changes in the distribution of bottom sediments, changes in the functions of coastal ecosystems and impacts on human activities.
There are emerging estimates of the physical impacts and economic costs to coasts in Europe from sea level rise and flooding from storm events. Impact results using the DIVA database and models produced from the DINAS-COASTS DG research project (DINAS-COAST Consortium, 2006; Hinkel and Klein, 2007; Nicholls et al., 2007a; Vafeidis et al., 2004; 2007) have been developed for Europe in the PESETA project (Richards and Nicholls, 2007). They show impacts increasing dramatically without adaptation: in the 2080s under the A2 SRES scenario (sea level wil rise 0.23m-0.51m at 2090-2099 relative to 1980-1999) some 19 000 km2 of land in Europe could be permanently lost, potentially affecting some 1.4 million people in Europe experiencing flooding each year, and with an estimated economic costs of 18 billion euro/year .
The most threatened coastal environments within Europe are deltas, low-lying coastal plains, islands and barrier islands, beaches, coastal wetlands, and estuaries. Tidal range is a key factor: in general, the smaller the tidal range, the greater the susceptibility to a given rise in sea level. The Mediterranean and Baltic coasts have a low tidal range (<1 m), which suggests that they will be more vulnerable to sea-level rise than the Atlantic Ocean and North Sea coasts (Nicholls and Mimura, 1998). Habitats could be severely reduced or even disappear during the 21st century because of the low tidal range in these areas and the limited scope for onshore migration, which is due to the intense human use of the coastal zone (Nicholls and Klein, 2003a; Alcamo et al. 2007).
The ocean response to global warming with a sea-level rise, amounting to [+3mm/yr] at present, and the ice melting has been possible to be measured accurately, and unequivocally by satellite altimeters all over the world. Here, an orbiting satellite emits electromagnetic waves to the surface of the Earth. It then records the reflected signals and their time of arrival. From these altimetric measurements, the range from the satellite to the sea and/or water surface can be determined precisely and with respect to the centre of mass of the earth.
Altimeter data have assisted in monitoring sea level changes world wide, but also in forecasting high seas, and in improving operational oceanography (forecasting eddies, etc.) as well as monitoring basin-scale variability in the oceans. Moreover, ocean surface topography with altimetry provides data for operational forecasts ranging from tides and marine ecosystems to human health and safety.
The expected operational time of altimetric missions is however limited; for example it does not commonly exceed 5 years (i.e. ERS-1 from July 1991 to June 1996). Also, the results from each altimetry mission, such as sea-surface heights and sea-anomaly fields, need to be continuously and independently connected onto a common and global reference system. Thus, to observe long-term trends in ocean changes and to distinguish patterns of natural variability, satellite measurements have to be calibrated and validated. Calibration and validation (Cal/Val) of altimetric missions is the process of quantitatively defining and comparing the altimetric systems measurements against well understood and accurately determined in-situ measurements that are independent from the altimeter. The possible altimeter sources of error including the sea state bias, wet tropospheric path delay, marine geoid, tides, and geographically correlated errors are also determined through satellite altimetry calibration.
Calibration is primarily provided by permanent calibration facilities (Cal/Val sites), or by a network of globally distributed tide gauges. Each calibration method presents advantages and disadvantages. For example, permanent Cal/Val sites provide absolute altimeter biases as well as cross-calibration among different satellites, while distributed tide-gauge networks result only in relative bias determination among missions.
The absolute bias of satellite altimetry measurements is, more often than not, determined by permanent calibration facilities (Cal/Val sites) established at dedicated sites all over the globe. In the world, there exist four permanent Cal/Val facilities. Two of those sites are located in Europe (Gavdos in Greece operated by the Technical University of Crete and Corsica in France operated by OCA/CNES), one installed in the USA (Harvest Oil Platform Experiment, California, operated by JPL/CalTech, USA) and the last one set up in Australia (Bass Strait, Tasmania, operated by the University of Tasmania). This SOFIA Project has contributed into the infrastructure enhancement of this Gavdos Cal/Val site.
Current and future altimetric missions (i.e. Cryosat-2, Sentinel-3, etc.) seem to extend the usage of altimetric products to new applications by incorporating novel measuring techniques (i.e. Delay Doppler, wide swath) and unique sensors (i.e. Ocean Land Colour Instrument in Sentinel-3 of ESA). Thus, satellite altimetry is also considered to be an essential tool for estimating river discharges, surface water extent, height and slope, volume change in lakes, flood forecasting and fresh water detection.
Regional and local sea-level rise in Europe generally will differ from the global average because, for example, of vertical land movements (glacial isostatic rebound, tectonic activity, and subsidence). Deviations will also occur as a result of local oceanic effects, such as changes in oceanic circulation, water density, or wind and pressure patterns. Hence, the geographical distribution of satellite altimeter errors must be known. This knowledge is what the proposed project enables with the combined observation of vertical land movements (GNSS data interpretation) and sea level monitoring (tide gauge data).
Upon the completion of the SOFIA project, GeoMatLab has been able to provide calibrated and validated data, information and knowledge to better understand, and assess the Earth, its sea level and its climate.
Social impacts of the SOFIA project are important in the sense that GeoMatLab takes steps in the right direction to understand the geodynamic phenomena associated with the active earthquake zone, providing improved knowledge, which eventually could provide earthquake risk mitigation for the society.
The establishment of a permanent continuously operating tracking network acts as a catalyst in determining the requirements and technical specifications for the recording of multi-disciplinary geo-information. The real-time detection of land deformation changes will especially contribute to understanding the earthquake mechanisms in the area and the relevant crustal motions in a continuous fashion.
The social benefits will be the stimulation of geodynamic and geotectonic research from the point of view of economic and social cohesion, and last but not least, the stimulation of development of a data base with geodynamic, sea level change, geodetic and seismic measurements which will be the basis for future researches in the area.
Another important task of the SOFIA support action is its multi-disciplinary geo-informatic approach at an active geotectonic area. This particular character of the joint program allows the modelling of the dynamics of the area under study and therefore will help in reducing the seismic hazard, contributing subsequently significant social and economic benefits.
2. Synergy with Cohesion Funds
On 5 November 2007, the European Commission approved the Operational Programme Crete and the Aegean Islands. It involves Community support for 3 NUTS II regions of the Greek Islands: Crete, the North Aegean islands, and the South Aegean islands. The three regions covered by the Operational Programme have a rich environment, the potential to generate income from high-quality tourism, important international infrastructure connections (particularly for sea transport), diversified tourist assets as well as some distinguished research centres and universities. Apart from the South Aegean region, however, regional GDP per capita and employment rates are below the national average.
The major financial public investment efforts undertaken in 2007-13 are aiming to:
diversify the economic base of the tourism sector into higher-quality market segments and innovative approaches;
provide enhanced infrastructures to improve accessibility;
promote sustainable development through increased emphasis on the environmental dimension of all actions;
provide environmental infrastructures, nature protection and the proper management of natural resources;
utilise the natural and cultural heritage within the context of sustainable growth;
promote digital convergence and entrepreneurship;
combat intraregional disparities, notably in the South Aegean region.
Along these lines, the SOFIA Project activities rhyme along to:
provide environmental infrastructures (i.e. the scientific equipment installed in Gavdos and western Crete to calibrate satellite altimeter and monitoring crustal deformation);
promote digital convergence and entrepreneurship (priority axis 4) through the improvement of the Technical University of Crete infrastructure and development of innovate products (i.e. the development of a prototype instrument for the calibration of Cryosat-2 and Sentinel-3 altimeters);
contribute to sustainable development and quality of life (priority axis 7) through the protection of environment (monitoring of environmental parameters related to earthquake risk prevention and tsunamis warnings);
contribute to the goal of income generation through exploitation of its results for high-quality tourist, archeological and surveying applications in Crete;
creation of two new jobs, conservation of other four and creating the conditions for recruitment of more researchers;
improve of the scientific excellence of the region (according to the Innovation Scoreboard 2006 methodology Region of Crete takes the 174th place of a total of 203 EU-25 regions)
improve participation of the Technical University of Crete in RTD projects (TUC participated in 12 RTD projects financed from the Operation Programme Competitiveness 2000-2006; Source General Secretariat of Research and Technology).
It is clear that the activities that have been implemented through SOFIA project are in line with the European funding directions, like ERDF and the Cohesion Fund, and the Operational Programme Crete and the Aegean Islands.
3. Dissemination Activities
A Technical Workshop on Satellite Altimetry Calibration & Deformation Monitoring with GNSS has been organised by GeoMatLab on 20-21 January 2011. The workshop took place at the Center of Mediterranean Architecture, Old Venetian Harbor, Chania, Crete, Greece. Invitations for participation have been sent to top-class researchers. Representatives from all partnering organizations participated in this meeting. Conclusions and Recommendations drawn from the Crete Workshop in Chania, 20-21/Jan/2011, have been as follows:
1. All satellite calibration/validation world sites should aim at two objectives: a) To report on the satellite altimeter bias and their byproducts, as users will directly apply these to get unbiased altimetry products; b) to try new corrections-algorithms to improve future altimetry products and provide more insight into the origin of errors and biases.
2. All satellite altimeter Cal/Val sites in the world (Corsica-France, Gavdos-Greece, Harvest-USA, Bass Strait-Australia) should make an effort to homogenize solutions and results. Homogenisation may entail the following actions: a) All Cal/Val sites should apply common processing strategies and loading models (tides, atmosphere etc,) for their GNSS data to produce comparable results in a common world reference system using the same world GNSS/IGS reference sites; b) The coordinates and velocities of their Cal/Val reference sites should be tied to the same global frame (i.e. center of mass of the earth); c) GLONASS measurements as well as GPS data is recommended to be used in their GPS reference site solutions; d) Different software, such as Bernese, GIPSY, GAMIT should be applied for precise positioning solutions of the reference sites; e) For the ionosphere corrections, GDR dual ionospheric corrections should be used, instead of GPS ionosphere modelling; f) The wet troposphere corrections, based on local GPS, should serve for comparison and to cross-validate satellite results. Radiometer corrections used over the whole ocean must be used for continuity. Investigations using local GPS give insight on the error budget in coastal areas. Development of new algorithms (e.g. S. Brown) and/or new instruments is strongly encouraged to avoid land contamination; g) Retracking is also an important issue when satellites are approaching the coasts and should be applied; i) Looking at 18/20 Hz to assess quality of waveforms (that can impact estimates of ranges); j) Open ocean SSB models are not valid in coastal regions. The SSB correction may require further investigation, for example development of local models, use of instruments to measure wave, swell, new parameterisations to capture increased non-linearity of waves, etc. The SSB is intimately linked to waveform retracking, e.g. coastal wind sheltering will cause specular waveforms that affect retracking performance; k) Cal/val can benefit of advances in coastal altimetry, especially exploiting coastal-GDRs (from PISTACH, COASTALT, CTOH initiatives).
3. When calibrating satellite radar altimeters with GPS buoys, then: a) GPS heights should be determined with the antenna radome on and off to determine biases in heights and systematic errors before deploying the buoy on the sea surface. These tests can be conducted on ground for long period (at least 1 day); b) In a GPS-buoy campaign, accelerometers may be installed to determine the significant wave heights and thus the sea-state bias; the SWH can be also determined by the raw movement of the buoy after applying a low-pass filtered time series.
4. Atmospheric loading effects are of the order of sub-cm;
5. Geoid heights and local measuring conditions may be shared by all Cal/Val sites;
6. Digital Elevation Models are useful to have in altimetry calibration. Phillipa Berry may help in that direction for ACE2 and details.
7. TIGA processing and analysis should be re-activated and all Cal/Val sites should be re-processed.
8. The IGS does not maintain a public archive for all GNSS sites. More precise positioning solutions are required by the Cal/Val sites.
9. Transponder calibration algorithms and procedures should be investigated for the new altimetric missions as well.
Participants from Australia, Germany, France, Hungary, Italy, Greece, Denmark, etc. took place in this International Workshop.
A Regional Outreach Workshop on "GeoMatLab's contribution to local and regional capacity building" has been organized by the Geodesy & Geomatics Engineering Lab of the Technical University of Crete. This Workshop took place in the city of Chania, Crete, Greece, on 1st July 2011.
The purpose of this Regional Outreach Workshop was to inform local, regional and national authorities for the results obtained so far by the REGPOT project SOFIA and the way that these results might be further exploited to contribute to regional sustainable development. Top scientists and stakeholders have been invited to participate in this Outreach Workshop. Also, there was a Session dedicated to the presentation of upcoming Call for Proposals under the framework of the "Regions of Knowledge", "Research Potential" and "Ideas" programs. A round table discussion for better exploitation of Structural Funds for Research and Technological Development also took place.
Besides the organization of these workshops dissemination of the SOFIA project has been acquired through the establishment of the projects website (http://www.geomatlab.tuc.gr/lab-projects/sofia) participation of GeoMatLab personnel in international conferences and workshops while dissemination of SOFIA project results to the general public has been performed via interviews and article publications in regional and national mass media.
10. Exploitation of SOFIA project results
The significant improvement of GeoMatLabs visibility at the international scientific community has been realised through the previously mentioned dissemination activities as well as the publication of several peer-reviewed articles in scientific and conference proceedings. The research quality of these publications as well as the attendance of GeoMatLabs in a number of international conferences were the main reasons why international organisations and stakeholders (besides the SOFIA partnering organizations) expressed their interest in collaborating with GeoMatLab (i.e. India and China).
More specifically, negotiations with the satellite operators, such as ESA, are under way for funding the establishment of a permanent calibration site for Sentinel-3 in the south west of Crete using the developed transponder. A site with a triple cross over of the Jason, Sentinel-3A & 3B and AltiKa satellites over west Crete has already been identified, tested, and selected. These initiatives have been formally announced by ESA.
In the same token, a permanent site at CRS1 in southwest Crete has been set and planned for the calibration of the Chinese HY-2 satellite altimeter and collaboration with the First Institute of Oceanography, State Oceanic Administration, China. This collaboration will be further enhanced through the FP7-PIRSES-GA-2012-318950 project entitled: CALT: A global network of permanent sites for calibrating satellite altimetry missions coordinated by GeoMatLab. The French Partnering Organization, OCA, as well as the University of Amazon, Brazil also participate in this project. It will start on October 2012. GeoMatLabs collaboration with the Chinese altimetric community will be further enhanced if the proposal submitted under the framework of a bilateral Greece-China Call, entitled: SPARKLE: Innovative Technologies for Calibrating Satellite Altimeters using prototype instruments of microwave transponders and integrated GNSS buoys is selected to be founded (evaluation results are pending).
The work conducted for abrupt change detection and deformation monitoring will be further exploited, because the developed algorithms will be implemented for the identification of landslides in highways under the framework of the project ISTRIA: Development of an Integrated System for Rockfall Identification in highways that was recently (August 2012) approved for funding from the Greek General Secretariat for Research and Technology. The precise positioning data provided by the established GNSS TUC-net array is being used by local engineers to improve their accuracy and operations cost. Finally, the establishment of the first Greek EGNOS station as well as the first European BeiDou/Compass receiver inside the University Campus will further promote GeoMatLabs research capacity and contribution to regional development providing that, especially, EGNOS has numerous application directly related with societal needs like navigation of vehicles, aircrafts and ships and with search-and-rescue applications.
Finally exploitation of SOFIA project results is expected to occur through the collaboration that GeoMatLab has initiated with public (i.e. Greek Cadastre, Region of Crete) and private (i.e. PRISMA Electronics, General Consulting ISTRIA SA, AGA Hellas) entities.
List of Websites:
http://www.geomatlab.tuc.gr/lab-projects/sofia
The Laboratory of Geodesy and Geomatics Engineering (GeoMatLab) at the Technical University of Crete in Greece is located in Crete, one of the EUs convergence regions, but is a dynamic and developing scientific entity on a European and international scale. Its research activities are on the Global Navigation Satellite Systems, satellite geodesy and deformation monitoring, and on satellite altimetry calibration and validation (Cal/Val).
On the Gavdos island, 40 km south of Crete, the GeoMatLab has established in 2001 and has been operating continuously, as of 2004, a permanent calibration facility for satellite radar altimeters. Four permanent sites exist in the world for providing such absolute calibration of satellite altimeters. Also, GeoMatLab operates a network of continuously functioning GPS reference stations in the western Crete and Gavdos, one of the most active seismic zones in Europe.
Because of its geographical location, GeoMatLab was not able to attract top researchers to boost its scientific excellence and drive it to multi disciplinary research. The infrastructure installed so far needed to be upgraded to keep up with the continuous technological advancement and challenges in altimetry and deformation monitoring. The objectives of this SOFIA project were directed into:
Reinforcing GeoMatLabs research potential through recruitment of senior and junior researchers.
Mobilizing Lab personnel for building its scientific and research capacity;
Developing partnerships with EU research entities with similar scientific interests.
Participating in research projects for scientific advancement and sustainability;
Contributing to regional economic and social sustainable development.
Within the SOFIA Project, modernization and up-scaling of the infrastructure for satellite altimetry calibration and tectonic deformation monitoring have been completed in Gavdos and Crete, Greece. New equipment have been procured and installed at several field sites as well at the central facility in the Laboratory. Recruitment of post-doc researchers resulted in software development to estimate altimeter bias using in-situ and satellite altimeter observations. The applied calibration methodology has been the result of the cooperation with the OCA (France) partnering organization as well as with the other satellite calibrating institute in the USA, i.e. the Jet Propulsion Lab.
In collaboration with the Austrian SRISG partnering organization and ESA as well with CNES (France), a new prototype microwave transponder for calibrating satellite altimeters has been developed and delivered in 2011. This prototype instrument has tremendously enhanced the research capacity of GeoMatLab. Calibration procedures using the transponder are now developed as a result of the collaboration between SRISG and CNES, as well as ESA. Plans are under way for the calibration of the ESA satellites, Cryosat-2 and the upcoming Sentinel-3, as well as the Chinese satellite HY-2 and the French/Indian mission of SARAL/AltiKa using Gavdos and Crete Cal/Val facilities.
As a result of the cooperation with the German partnering organizations (GFZ and DGFI), data from the established GPS sites in Crete and Gavdos are routinely processed using three independent software packages, i.e. GAMIT, GIPSY, and Bernese, for monitoring crustal movements and parameters for the troposphere and ionosphere, but also for determining parameters in the satellite altimeter calibration. Permanent sites for the European EGNOS and the Chinese navigation system of BeiDou/Compass have been established in Crete and enabled GeoMatLab to extend its operations into other international navigation satellite systems.
Collaboration with the SOFIA partnering organizations enabled us to improve the satellite altimetry calibration methodology, as well as the GNSS data processing techniques and efficiency for crustal deformation monitoring.
Project Context and Objectives:
The Laboratory of Geodesy and Geomatics (GeoMatLab) at the Technical University of Crete in Greece is located in Crete, one of the EUs convergence regions, but is a dynamic and developing scientific entity on a European and international scale. The primary focus of its research activities are on the Global Navigation Satellite Systems, on satellite geodesy and crustal deformation monitoring using geodetic data, and on satellite altimetry calibration and validation.
On the small island Gavdos, 40 km south of Crete, the GeoMatLab has established in 2001 and has been operating as of 2004 a permanent calibration facility for satellite radar altimeters. The location of the frontier land of Gavdos constitutes a strategic point for the calibration of satellite altimeters on a world level, and also for monitoring absolute sea level and climate change on a continuous and long-term basis. Four permanent sites exist in the world for providing absolute calibration of satellite altimeters. Three of them are located in Europe (Gavdos in Greece, Corsica in France, Ibiza in Spain is used intermittently), one in the USA (Harvest Oil Platform, California) and one in Australia (Bass Strait, Tasmania).
A competitive advantage of the Gavdos calibration infrastructure is its strategic location in the center of East Mediterranean and some of the special instruments installed at the facility. Dedicated calibration sites, such as Gavdos, which are located on a cross-over point and exactly under their repeating orbits of Jason satellite series, will continue to provide a vital service for modern altimetry missions. If on-site instruments however would not have been upgraded for the future Jason missions and not adjusted to the new challenging measuring techniques, such as the swath altimetry, the Gavdos facility would have been threatened to cease to provide its unique services to the worldwide altimetry community.
Furthermore, the GeoMatLab has been operating a network of continuously functioning Global Navigation Satellite Systems (GNSS) reference stations (CORS) located in the western Crete and Gavdos. Most of these stations are collocated with tide gauges. In addition, the CORS station named TUC2 has been part of the European Reference Frame Permanent network (EPN) as of June 2004 and was officially the first such EPN station in Greece.
Algorithms and software have developed by GeoMatLab for controlling and monitoring the quality of the satellite geodetic data, as well as for monitoring crustal deformation in Crete, which is one of the most active seismic zones in Europe. This has been performed with the use of dedicated GNSS arrays.
Participation of GeoMatLab in scientific organizations such as the European EUREF permanent network, the Ocean Surface Topography Science Working Team of the Jason satellite mission, the Calibration Validation Research Team of ESA, as well as the collaboration with European and international experts revealed that despite the strengths of the GeoMatLab, there were specific activities that should have been performed to enhance its scientific potential and operational capabilities for satellite altimetry calibration and deformation monitoring. Because of its geographical location in one of the EUs convergence regions, GeoMatLab was not able to attract top researchers to boost its scientific excellence and drive it to multi disciplinary research. The infrastructure installed so far needed to be upgraded to keep up with the continuous technological advancement and challenges in altimetry and deformation monitoring. The GeoMatLab was unable to purchase or develop prototype instruments (such as the transponder) by its own resources to meet the growing needs of future altimeters. Participation and funding from European programs was a necessity to ensure continuous operation of this important site located in a less advanced region of the EU.
Along these lines, the objectives of SOFIA project were as follows:
(1) The first objective aimed at developing strategic partnerships with well established European research entities and in particular: (a) the Observatoire de la Cote d'Azur (OCA), France, which has been running the Corsica Cal/Val site with knowledgeable and experienced research teams and the support of the French Space Agency (CNES: Centre National dEtudes Spatiales); (b) the Space Research Institute of the Austrian Academy of Sciences which has experience in calibrating altimeters using dedicated microwave transponders. Thus, the know-how existing in the Space Research Institute for transponder data analysis would be transferred to the less advanced region of Crete; (c) the Deutsches Geodätisches Forschungsinstitut (DGFI) in Munich, Germany to exchange know-how and experiences for automating the monitoring of crustal deformation of West Crete using the existing GNSS arrays; and the GeoForschungsZentrum(GFZ) in Potsdam, Germany for the exchange of experiences for replacing expensive radiometric measurements with dedicated instruments at Gavdos Cal/Val site with the GNSS zenith troposphere delays.
(2) The second objective was to enhance the Gavdos Cal/Val present capabilities by developing new calibrating instruments and procedures, so that GeoMatLab was prepared for the calibration of future altimeters, such as the European Cryosat-2 and Sentinel-3, through a collaboration with the European Space Agency;
(3) The third objective was to reinforce its research potential by recruiting at least two new researchers: one to carry out research on geodetic signal monitoring methodology and software development and another to enhance satellite altimetry calibration procedures and instruments;
(4) The fourth objective was to perform dissemination and promotional activities to increase GeoMatLabs visibility. This had to be done with the organization of two outreach workshops: one international on satellite altimetry calibration and deformation monitoring with invited international experts and stakeholders, and another regional to inform local and regional authorities on the ways that Structural Funds could be used to exploit GeoMatLab research results for regional social and economic development.
Within the SOFIA Project, modernization and up-scaling of the infrastructure for satellite altimetry calibration and tectonic deformation monitoring have been completed in Gavdos and Crete, Greece. New equipment have been procured and installed at several field sites as well at the central facility in the Laboratory. Recruitment of post-doc researchers resulted in software development to estimate altimeter bias using in-situ and satellite altimeter observations. The applied calibration methodology has been the result of the cooperation with the OCA (France) partnering organization as well as with the other satellite calibrating institute in the USA, i.e. the Jet Propulsion Lab.
In collaboration with the Austrian SRISG partnering organization and ESA as well with CNES (France), a new prototype microwave transponder for calibrating satellite altimeters has been developed and delivered in 2011. This prototype instrument has tremendously enhanced the research capacity of GeoMatLab. Calibration procedures using the transponder are now developed as a result of the collaboration between SRISG and CNES, as well as ESA. Plans are under way for the calibration of the ESA satellites, Cryosat-2 and the upcoming Sentinel-3, as well as the Chinese satellite HY-2 and the French/Indian mission of SARAL/AltiKa using Gavdos and Crete Cal/Val facilities.
As a result of the cooperation with the German partnering organizations (GFZ and DGFI), data from the established GPS sites in Crete and Gavdos are routinely processed using three independent software packages, i.e. GAMIT, GIPSY, and Bernese, for monitoring crustal movements as well as parameters for the troposphere and ionosphere, but also for determining parameters in the satellite altimeter calibration. Permanent sites for the European EGNOS and the Chinese navigation system of BeiDou/Compass have been established in Crete and enabled GeoMatLab to extend its operations into other international navigation satellite systems. Collaboration with the SOFIA partnering organizations enabled us to improve the satellite altimetry calibration methodology, as well as the GNSS data processing techniques and efficiency for crustal deformation monitoring.
The scientific results obtained so far within the SOFIA project, have been presented at several international workshops and conferences, such as the Ocean Surface Topography Science Team meeting, the ESA Cryosat and ICESAT meeting, the SPIE Conference, the ESAs Living Planet Symposium, the Week of Innovative Regions 2010, etc. Six scientific papers have been published in the Marine Geodesy and the Advances of Space Research journals. In addition, the GeoMatLab personnel attended short training events in GNSS data processing (organized by INGV, Italy), in satellite altimetry and GIPSY software for precise point positioning (organized by JPL, USA) and in satellite radar interferometry (organized by Terrafirma, Italy). Participation in summer schools organized by the International Association of Geodesy and the European Space Agency also increased GeoMatLabs visibility and improved its research capacity. Involvement in international research teams as principal investigators (i.e. the Cryosat-2 and SARAL/AltiKa calibration-validation research teams) enhanced the Labs visibility and offered the possibility for participating in forthcoming research projects.
Strategic collaborations with national (i.e. the Greek Cadastral, Leica Company, etc) to jointly make use of the GNSS arrays throughout the country and involving the network developed in the SOFIA project, as well international Partners have been established. Besides the International Conference, Meetings for the visibility of the GeoMatLab, strategic partnerships of GeoMatLab with international Organizations have emerged, such as the Indian Space Research Organization, European Space Agency, French CNES Space Agency, the Chinese First Institute of Oceanography and the Chinese GNSS Research Center, Wuhan University, China.
After the completion of this Project, the methodology and facilities at the Gavdos and Crete for the calibration of satellite altimeters have improved and were made capable to be extended for other international altimetric satellites using alternative and independent techniques, but also newly developed instruments. Collaboration with all partnering organizations that took place during this reporting period have resulted in long-term associations by signing 3 Memorandum of Understandings with the Austrian, German and French Partnering Institutes.
GeoMatLab has built and established its caliber and capacity within the international community and research teams for satellite calibration and deformation monitoring. It also enhanced its research potential and visibility. The dedicated Gavdos and Crete Cal/Val facilities have established as one of the four international satellite calibration sites in the world.
The established dedicated Cal/Val site is now fully instrumented to provide an independent (in-situ) determination of sea-surface observations and provide the basis for calibrating the altimetric measurements made by the satellites as they overfly the location. It will provide fundamental calibration information in the centre of the East Mediterranean for an uninterrupted monitoring of the Jason satellite and its successors, as well as the European Cryosat-2, and Sentinel-3 and Chinese and French/Indian missions. Also, the established permanent GNSS network in west Crete and Gavdos is able to monitor crustal deformation in one of the most seismic active regions in Europe on a continuous basis and provide valuable information for earthquake research and interpretation. This site has become essential infrastructure in monitoring sea level variations and climate changes for our planet.
Project Results:
Description of the main S&T results/foregrounds (max length 25 pages)
The work performed during the SOFIA project led to the accomplishment of all foreseen project objectives. The GeoMatLabs international visibility has been significantly enhanced leading to the establishment of strategic partnerships with European (i.e. SOFIA Partnering Organizations, European Space Agency, CNES (French Space Agency), Danish Technical University, Danish Space Center) and international Institutes (i.e. Indian Space Research Organization, First Institute of Oceanography-China, Chinese Global Navigation Satellite Systems Center-Wuhan University, China). The research capacity of GeoMatLab has been built up by its research staff and the established infrastructure is capable and ready for cutting-edge research on satellite altimetry calibration and ground deformation monitoring. The Laboratory now possesses a research infrastructure that is unique not only in regional/national but also at international level. To this end, the established scientific excellence of the GeoMatLab research team in conjunction with the developed infrastructure led to overcome its disadvantage of being located in a convergence European region and achieve results that match those performed at research institutes located in more advanced countries.
The scientific and technological results accomplished during the 42 months of this Project duration can be grouped into: a) infrastructure modernization and up-scaling, and b) research capacity enhancement. These S&T results have been properly disseminated into public and private entities and stakeholders (a description is given in the next Section) and their exploitation is expected to secure funding of the GeoMatLab activities for the upcoming years.
The following Sections describe in detail the scientific and technological results of the SOFIA project, as well as the activities performed that allowed the establishment of strategic partnerships.
1. Infrastructure modernization and up-scaling
The developed infrastructure has been distributed at several sites over Gavdos and west Crete, Greece. The Operations Control Centre is located in the TUCs campus and has been developed for fast and efficient processing, as well as for data archival, and for controlling the field units. Next to the Operations Control Center also exists a permanent and continuously operating Global Positioning System (GPS) station, named TUC2, operating as of 2003. This station is part of the European Permanent Network for EUREF. A new EGNOS station, coined TUC3, has been installed in the University Campus and is the first EGNOS site in Greece. TUC3 is collocated with a BeiDou/Compass chinese satellite station (TUC4). BeiDou is the Chinese navigation system and this TUC4 site is the first one to be installed in Europe. Collaboration with the Chinese GNSS Research Center, Wuhan University, China, made this installation possible. GeoMatLab personnel are currently trained by Chinese researchers in processing BeiDou satellite data with the PANDA software.
The main satellite calibration facility is located at Gavdos island; on land property, bought by the University for the needs of satellite calibration. The Gavdos calibration facility includes the Karave (tide gauges, meteo sensors, GPS, etc.) on the harbour, the Theophilos (central communication site and control) and the DIAS sites (transponder). The RDK1 site on the south Crete is considered to be a secondary Cal/Val site, because it has been installed along the north part of the ground track of the Jason satellites. In south west Crete, the Chrysoskalitissa site (CRS1) has been upgraded and is currently a fully-equipped Cal/Val site (GNSS receiver, main and back-up tide gauge, meteorological sensors, etc.) ready to be used for the calibration of the Jason series and the Chinese HY-2 satellite altimeter.
The deformation monitoring network in west Crete has been also enhanced through the establishment of the SUG1 GNSS site in south west Crete. This SUG1 site, as well as the previously established sites at Petra Seli and Menies (SEL1 and MEN2, respectively) concluded the GNSS network for monitoring any velocity transient effects and other phenomena of the earths crust at the subduction zone in Crete. All these GNSS sites have been upgraded with the state-of-the-art, reliable, and accurate scientific instrumentation.
The basic equipment and software that has been purchased, installed and operarate during the SOFIA project is as follows:
Three GNSS receivers. The first one is a receiver capable to lock data from the European Geostationary Navigation Overlay System (EGNOS) and the other two are state-of-the-art units that replaced the old ones operated for several years. More specifically the EGNOS receiver has been installed inside TUC campus in a remote area dedicated for the development of the first EGNOS Data Collection Station in Greece. One of the new receivers replaced the old one operated at the TUC2 site (now transferred and installed at the Rodakino site in south Crete) while the second one (GVD8) replaced the one operated at the Gavdos Karave site (GVD5);
Six tide gauges. Four of them have been installed at the main satellite calibration location in Gavdos, i.e. Karave site, while the other two have been set-up at the Chrysoskalitissa site in southwest Crete. More specifically, at the Karave site a pressure tide gauge (KVR5), an acoustic tide gauge (KVR4) and a radar tide gauge (KVR6) have been installed and are fully operational. The later tide gauge (KVR6) has been setup inside the Karave concrete shack in the Gavdos harbor, where inside it there exists a well for reliable sea level measurements. This installation has been carried out to have a protected sea level measuring system that will not be influenced by weather conditions, and thus it will provide reliable measurements for the sea surface height. On-site calibration of the sea-level measurements obtained by these tide gauges will be made by a staff gauge also installed there at the harbor. In south west Crete, the Chrysoskalitissa Cal/Val facility has been equipped with one pressure (SVR1) and one radar tide gauge (SVR2). This site will be used for the calibration of the Chinese HY-2 satellite altimeter and is expected to play a dominant role in future GeoMatLabs scientific and research activities. It will be the first time that this Chinese satellite altimeter will be calibrated by a European institute and outside China;
Three meteorological sensors. For the Chrysoskalitissa and Gavdos Karave sites meteorological sensors, directly connected directly to GNSS receivers (thus ensuring data transfer through GNSS raw data), have been purchased and installed. Additionally, the old meteorological sensors installed at the Gavdos Theophilos site have been re-calibrated in the Lab and replaced, when damaged;
One choke ring GNSS antenna. This has been installed at the Chrysoskalitissa CRS1 GNSS site in GeoMatLabs effort to improve precise geodetic positing at this site to meet the satellite altimeter calibration standards;
One prototype instrument for monitoring ionospheric scintillations;
Software for GNSS data processing. GeoMatLab is now performing GNSS data processing using different software. The newly acquired software (BERNESE) can produce Total Electron Content estimates for the ionosphere.
Batteries for operation of the GPS buoys, used for measurement of the sea surface height simultaneously when the Jason-2 satellite was flying over the boat at sea. These buoys are property of the Hellenic Centre for Marine Research but were lend to the Lab for the purpose of this Project.
Modems, cables and other peripherals for the communication links. Currently there are two satellite links (at Gavdos Theophilos and Chrysoskalitissa sites) and two mobile telephone GPRS connections (at Gavdos Karave and Rodakino sites).
One file-server main computer. This computer has been placed in a protected environment at the major TUCs Data Center on Campus, and is used for data archival, data base operation, data processing, etc;
Two personal computers and notebooks with their peripherals. These computers were by the Project Secretariat and the recruited post-doc researchers, while the notebooks have been used in the field for in-situ data downloading.
Software upgrade for remote, automated GNSS data management;
Solar panels and accessories for power supply at the MEN1 GNSS site as well as the EGNOS site;
Replacement of the batteries used for power supply of the Gavdos main facility;
The current state of the GeoMatLabs infrastructure is presented in the following Sections.
1.1. TUC Campus Facilities
The instrumentation installed at TUC Campus facilities are:
A Leica GNSS 1200+ receiver (named TUC2) along with a Vaisala PTU 200 meteorological station.
A PolaRx3eGPRO EGNOS/GPS station (called TUC3).
A UNICORE UB240 CORS Compass/GPS station (called TUC4).
The TUC2 station is installed inside a concrete shack close to the GeoMatLab's facilities. TUC2 is part of the European Reference Frame (EUREF) regional GNSS network since 2004. Its data are available on line in the internet as part of the permanent European GNSS net (http://www.epncb.oma.be/_trackingnetwork/siteinfo4onestation.php?station=TUC2). TUC2 station provides to EUREF hourly and daily GPS (American) and Glonass (Russian) data as well as meteorological measurements. Users can access data through the EUREF ftp servers (ftp://igs.bkg.bund.de/EUREF/obs/2010).
The TUC3 is installed inside a different concrete shack close to the Laboratory's facilities on Campus. TUC3 station is operated as a permanent GNSS station and therefore must follow the IGS (International GNSS Service) standards for CORS (Continuously Operating Reference Stations). This is also part of the EGNOS (European Geostationary Navigation Overlay Service) data collection network.
TUC4 station is the first European GPS/Compass GNSS station (Compass/BeiDou is the Chinese satellite navigation system). The receiver is temporarily installed on the roof of the Laboratory building for training and easy access.
A Meteorological sensor (Vaisala PTU200) is directly connected to the TUC2 GNSS receiver using a serial cable. In this way, the GNSS receiver acts as a data logger for the meteorological sensor. Measurements are stored in the widely used meteorological RINEX format inside the satellite receiver. The GNSS receiver is accessed using a TCP/IP interface (The university LAN network is accessible inside the concrete shack).
1.2. Gavdos Cal/Val facility
The following instruments have been installed at the Gavdos Cal/Val facility within the framework of the SOFIA project:
Karave site at the Gavdos harbor
The Karave site in Gavdos is the main site used for satellite altimeter calibration at the harbor. The instruments installed there are:
A Leica GNSS receiver, called GVD7A Paroscientific MET4 meteorological sensor, attached to the GVD7 receiver;
A back-up Leica GNSS receiver (GVD8). This state-of-the-art receiver measures the American GPS and the Russian Glonass signals as well;
An OTT Kalesto radar tide gauge (KVR3)
A General Acoustics LogALevel backup tide gauge (KVR4)
A Valeport tide master pressure tide gauge (KVR5);
A Vega radar tide gauge (KVR6);
A staff gauge for onsite calibration of the sea-level measurements made by all Karave tide gauges in the Gavdos harbor;
A LINUX downloading heavy-duty computer.
A GPRS communication link.
All sensor measurements (except KVR3) are downloaded daily and archived at the Thales main file-server computer in the University Campus in Chania.
Theophilos central site in Gavdos
The Theophilos site in Gavdos is the main satellite calibration infrastructure on Gavdos Island. All instruments placed there are located at a 4,000 m2 plot owned by the Technical University of Crete. Originally when there was only a poor UHF data connection to the island, all data transmissions where tunneled through Theophilos site at the Gavdos harbour and then to the University facilities in Crete.
The instruments installed are:
A Leica RS500 GPS Receiver along with a Leica AT504 GPS choke ring antenna comprise the GVD0 GNSS site;
An Aanderaa Automatic weather station has been calibrated in the Lab and replaced;
A DORIS Satellite beacon along with a Vaisala PTU200 meteorological station. (Owned and operated by CNES, France)
An industrial computer as well as the other sensors installed at this Gavdos Central facility;
Dias transponder site
The DIAS site in Gavdos is located under the crossover of Jason satellite Passes No 018 & 109. The old microwave transponder (property of the Austrian Partnering Organization) has been installed there since 2003. Under the framework of the SOFIA project, several GPS and geodetic leveling surveying have been conducted for a) determination of the transponders absolute ellipsoidal height, and b) estimation of the atmospheric delay parameters (wet troposphere and ionosphere) for correcting Jason-2 satellite altimeter measurements. The transponder has been disassembled and shipped from Gavdos to CNES French Space Agency in Toulouse for examination, calibration, and upgrading in June 2012. The site is to be occupied by the newly developed TUC transponder for the calibration of Jason satellites.
1.3. Rodakino Cal/Val facility: RDK1
The Rodakino Cal/Val facility is at the south central coast of Crete and under the ground track of the Jasons Pass 109. This facility serves as a back-up satellite calibration site and has been used to verify the altimeter bias results obtained by the Gavdos Cal/Val facility for the determination of the Jason-2 satellite.
A radar tide gauge station (RDK1, type: Vegapuls-61) with its accompanying data logger (Vegamet-624) and a Leica (Smart 6200) GPS receiver had been initially installed at Rodakino site on 6 March 2009. The GNSS receiver was then replaced with a Leica GRX1200GG PRO receiver and a Leica AT504 choke-ring antenna to enhance the sites performance. Data are transferred to the Operations Control Center in the University Campus via GPRS communications link.
1.4. Chrysoskalitissa Cal/Val facility: CRS1
A Leica GRX1200GG PRO GNSS receiver along with a Leica AX1202 GG antenna has been operating at Chrysoskalitissa site since 8 March, 2008. A Vaisala PTU300 meteorological sensor was installed on March 5 2010. A pressure tide gauge station (Valeport Tidemaster) has been installed on April 25 2012 (SVR1). An OTT RLS radar tide gauge was installed at Chrysoskalitissa site on June 2012 (SVR2). Data from this field measuring units are transferred via a satellite communication link to the Operations Control Center at GeoMatLab.
The Crysoskalitissa site will serve as the main calibration facility of the Chinese HY-2 satellite altimeter.
1.5. Other GPS sites for crustal deformation monitoring
GeoMatLab has installed three GPS sites in collaboration with the North Carolina State University, USA, along the direction of the North-South axis in Crete. These sites are equipped with Trimble NetRS GPS receivers and Trimble Zephyr Geodetic GPS antennas. Menies (MEN1) site was installed on 20 November, 2009 but was vandalized on 27 December, 2009. A new installation and a safer location has been chosen close and the station has been re-installed (MEN2). The Seli (SEL1) site in the central west Crete was installed on 10 July, 2009. The Sougia (SUG1) site in the south west Crete was installed on 5 November, 2010. The Technical University of Crete and the North Carolina State University, USA have signed a Memorandum of Understanding for scientific collaboration that led to the installation of three GPS receivers at the North-South axis of western Crete.
In order to be able to install and maintain these instruments at these remote field locations, several field trips have been carried out. For each field trip, a Traveling Report has been written and submitted. Moreover, details regarding the technical characteristics, operational capabilities, data storage and archival of the GeoMatLab instrumentation are provided in DL2.1 and its respective Annexes. This Section presented in detail the work conducted during the reporting period in terms of instrument maintenance, infrastructure upgrading, etc. All this work has been conducted under the framework of SOFIA project WorkPackage 2, Task 2.1.
1.6. Development of a prototype microwave transponder
The infrastructure presented in Sections 1.1-1.5 is considered to be the conventional equipment for the establishment of satellite altimetry calibration facilities and GNSS network for crustal deformation monitoring. During the SOFIA project, GeoMatLab was able to deliver a prototype microwave transponder to serve as an alternative and independent technique for calibration of satellite altimeters.
Microwave transponders have been proposed as an alternative tool for satellite altimetry calibration more than 10 years now. However, in the world, only few transponders have been built and implemented for this reason. In Europe there are only two active transponders: one is located in European Space Agency Observatory in Svalbard, Norway (more than 20 years old, mainly used for the Cryosat-2 calibration) and another old transponder in the Gavdos Cal/Val facility (more than 15 years old, property of the Austrian Partnering Organization). A microwave transponder is considered to be a stable and sharp calibrating target on the ground when the satellite flies over it, but it acts as if it were on the sea, yet with known properties. It receives, amplifies and retransmits, with minimal distortion, a satellite radar altimeter signal, which in turn is recorded on-board the satellite. The two-way travel time of the signal, after corrections for the atmosphere delays and tides, yields the range between satellite and transponder. This transponder can thus be used to calibrate the range measured by the satellite to the earth, the signal delays in the atmosphere and the effective cross section (sigma-naught) of the reflection in nadir-looking altimetry.
Under the framework of the SOFIA project, a prototype transponder has been constructed mainly for the calibration of the European Cryosat-2 and Sentinel-3 altimetric missions. As mentioned before the operation of a transponder relies on the reception by the satellite of an amplified signal produced by the transponder on land. However, satellite altimeters have specific thresholds in the signals power reception capability. If the satellite receives a signal above certain thresholds then it will be destroyed its sensors and possibly causing a damage of several million euros to the operational agency; in our case the European Space Agency. For this reason the specifications as well as the construction phases of the new ptototype transponder were set, specified, examined, and monitored by the responsible personnel (managers and technicians) for Cryosat-2 and Sentinel-3 missions in the European Space Agency.
The technical specifications of this new prototype instrument have been defined through joint efforts of GeoMatLab, ESA, CNES and the Austrian Partnering Organization. An invitation to tenders for the instrument manufacture had been then published in August 2009.
PRISMA Electronics SA is the industrial company, awarded the construction of the new transponder. Regular exchange of emails and teleconferencing between PRISMA, GeoMatLab and ESA, have been performed for continuous monitoring and review of the transponder manufacturing progress and to define technical details, not given at the initial technical specifications documents. Besides this communication exchange, meetings with ESA personnel in the Netherlands also took place.
A meeting at the European Science and Technology Center, ESA in Noordwijk, the Netherlands, took place on 26th August 2010 with representatives from ESA, PRISMA and GeoMatLab. The main purpose of this meeting was to monitor and review the progress on the transponder design/test/performance, but also cover some aspects about the location and the setting around the proposed calibration site in Crete.
The transponder has been delivered to TUC on 10 November 2010, however testing of its operational capabilities into simulated or real life conditions had to be conducted. There was a significant delay for the implementation of these tests, mainly due to the need for including some extra electronics parts and monitoring sensors inside the transponder. Moreover, there was a continuous inspection on the optimum transponder assembly, regarding the orientation of the transponders antennas and the way they were supposed to be placed outside the transponder itself. After a series of modifications and adjustments, the final transponder assembly with the mounted antennas has been agreed upon by ESA and finally manufactured by PRISMA private company.
Calibration and validation of the transponder itself, under simulated in-house conditions has been conducted at ESTEC/ESA specialized chambers in Noordwijk, the Netherlands. These specialized, in-house tests have been performed from March to June 2012. A meeting in ESA was arranged on March 2012 to evaluate the performance and review the newly developed prototype microwave transponder. The meeting took place in the ESA premises in Noordwijk, the Netherlands on Thursday 8-March-2012 and Friday 9-March-2012. In the meeting, a science team from ESA (Dr. Mavrokordatos, Dr. Borde and Dr. Rolo), a delicate of the manufacturing company, Prisma Electronics (Mr. Komninos) and the SOFIA Project Coordinator participated. During the tests conducted in ESTEC in the Netherlands, several problems have been encountered and resolved by ESA personnel. Finally, the transponder has successfully passed all calibration and verification tests and delivered to GeoMatLab in Crete in June 2012. Thus, Task 2.2 of the SOFIA project has been successfully accomplished.
2. Enhancement of GeoMatLabs research capacity
Section 1 presented the modernization and up-scaling of GeoMatLabs infrastructure as well as the construction of a prototype transponder instrument for satellite altimeter calibration. The existence of high-tech instruments is a precondition for the performance of cutting-edge research especially in engineering disciplines like satellite altimetry, satellite navigation systems and deformation monitoring. However, this is not enough and the researchers assigned to perform this Project research had to be well qualified. A main disadvantage of GeoMatLab is the difficulty to recruit experienced researchers because of its location at a convergence European region and the fact that the financial resources available are far less than in other more advanced countries.
To this end, GeoMatLab used the resources available from the SOFIA project to a) recruit three experienced researchers, and b) to build up the research capacity of existing team members. The latter was successfully performed through the exchange of know-how with the, the Indian Space Research Organization, The Jet Propulsion Laboratory, in the USA, the Chinese Research GNSS Center in Wuhan, The First Institute of Oceanography in Quigdao, China and certainly with the SOFIA partnering organizations, as well as the participation of GeoMatLab personnel in international conferences, workshops and training events. The following Sections will present the main results obtained during the SOFIA project lifetime in terms of improvement of GeoMatLabs research capacity.
2.1. Recruitment of experienced researchers
Three experienced (post-doc level) researchers have been recruited under the framework of the SOFIA project: two to enhance satellite altimetry calibration procedures and instruments and another to carry out research signal deformation monitoring methodology and software development.
One of the main activities in the GeoMatLab group is the calibration/validation of altimetry satellites. Such a work requires the development of algorithms that are using the data from the altimetry satellites, the data processing of GPS and the easy access and processing of data coming from on-site sensors, such as tide gauges. GeoMatLab installed a number of GPS stations and tide gauges in the Gavdos and south Crete areas which provided the required data to validate and expand the work on the satellite altimetry calibration and validation.
During the SOFIA project, improvement of existing and development of new algorithms in the satellite altimetry calibration/validation as well as the design and development of a software suite (called TUCaliBrit) were the main achievements regarding satellite altimetry calibration. This software uses data from the instruments installed at Gavdos facility (tide gauges, GPS receivers, meteorological sensors, etc.), apply several models (i.e. the marine geoid models, Mean Sea Surface, regression, filtering and prediction models) as well as the results from the GPS processing to determine the altimeter bias and corrections for other parameters of satellites flown over Gavdos. Currently, the user of TUCaliBrit has the possibility: i) to select among various marine geoid, mean sea surface and mean dynamic topography models, ii) to initialize the newly developed wet tropospheric model for coastal regions, as provided by Shannon Brown et al., and iii) to statistically analyze the extracted calibration results in order to choose the appropriate procedures and models that best fit the Gavdos Cal/Val local conditions.
The results obtained by the calibration methodology employed in Gavdos Cal/Val facility have been presented at relevant workshops (e.g. Ocean Surface Topography Science Team, Coastal Altimetry Workshops, etc.) as well as in scientific journals (i.e. Marine Geodesy, Advances in Space Research). The Gavdos Cal/Val facility has a proven record for reliable estimates of bias values in the satellite altimeters, which are in accordance with the values reported by the other three international calibration sites in the USA, France, and Australia.
Besides the conventional sea-surface calibration methodology, GeoMatLab also developed, in collaboration with ESA, CNES and the Austrian Partnering Organisation, a software suite for the determination of the Jason-2 satellite employing the existing Gavdos transponder. This software will serve as the main processing tool to analyze the data obtained by the newly developed prototype transponder.
Furthermore, through the collaboration with other Greek (i.e. Aristotle University of Thessaloniki, University of Aegean) and European (i.e. Danish Technical University) institutes the development of local geoid and mean sea surface models, to be applicable in Gavdos, was realized. These local reference models tend to reveal possible correlations between satellite altimetry data and sea floor bathymetry at the centimetre level. Also, the use of altimetric measurements for monitoring ionospheric disturbances caused by tectonic motion is under investigation at the subduction zone. This work is expected to be finalized in 2013 ans is not part of the SOFIA objectives.
Monitoring of tectonic motion present in the area of Crete was one of the main objectives of the second post doc researcher. To accomplish this Task the first step was to perform accurate, precise and reliable analysis of the GPS data obtained by the TUC-net GNSS network. During this reporting period this was feasible through the processing of geodetic data using 3 different scientific software (i.e. GAMIT, Bernese, GIPSY) that allow accurate determination of each station coordinates and the respective 3-dimensional rate of their movement.
Time series analysis of the data obtained by the GNSS array in Crete made feasible to identify long-range, power-law correlation in these geodetic data. Abrupt change detection algorithms for the identification of weak signals (possibly related to silent earthquakes) have been also developed and implemented in GeoMatLabs TUC-net geodetic data.
2.2. Exchange of know-how with partnering organisations
The SOFIA partnering organisation were: the Austrian Academy of Sciences (SRISG), Austria, the Observatoire de la Cote d Azur (OCA), France, the Deutsches Geodatiches Forschungsinsitut (DGFI), Germany and the GeoForschungsZentrum Potsdam (GFZ), Germany. The exchange of know-how with these well-established European entities was performed through dedicated visits, exchange of emails and teleconferences, meetings and organization of international conferences/workshops.
The main result of the collaboration between GeoMatLab and SRISG has been the development of the software to determine the Jason-2 altimetric bias using the SRISGs Gavdos transponder. This is an important asset in GeoMatLabs research capacity s that the developed technical skills are now to be used to exploit its newly developed, prototype transponder for the Jason-2 altimeter. Moroever, SRISG assisted significantly GeoMatLab to define the technical specifications for the newly developed transponder.
The collaboration between GeoMatLab and OCA-France focused on the conventional sea-surface calibration methodology. Advances on processing algorithms, models and statistical analysis of retrieved data were possible through this collaboration. Also, dedicated boat field campaigns for the determination of the instantaneous sea surface height as well as the geoid undulations slope at the Gavdos area have been conducted following recommendations provided by the OCA Partnering Organisation that has long-term experience in the performance of similar field campaigns.
The German Partnering Organisations assisted GeoMatLab to build up its research capacity in terms of GNSS data processing and crustal deformation monitoring. More specifically, the methodology to determine the wet troposphere and the ionosphere delay using the TUC-net GNSS array has been developed. These products are essential input in both calibration methodologies (sea surface and transponder calibration) employed by the GeoMatLab team. Processing of geodetic data using the Bernese software was feasible after specialised training events conducted by the German Partnering Organisations. Currently, geodetic data are processed by GeoMatLab employing three scientific software (i.e. GAMIT, Bernese and GIPSY) to provide reliable estimation of the coordinates and velocities of the TUC network in West Crete and Gavdos sites as well as the production of continuous time series of geodetic positioning solutions. These products are fundamental inputs for crustal deformation monitoring and abrupt change detection research.
Section 2 presented the work performed during the SOFIA project to enhance GeoMatLabs research capacity. A proof of this statement is corroborated by the GeoMatLabs publications record during the Project. During this 42 month of the SOFIA project, GeoMatLabs Project work was published in 13 peer-reviewed articles in scientific journals and workshop proceedings. In addition, 17 presentations (oral and poster) have been given at international conferences and workshops all over the world.
Summing Up
The main objective of this SOFIA project has been to improve the research capacities of GeoMatLab. This was performed through (1) the modernization of the infrastructure, (2) the development of a new prototype transponder instrument for satellite altimeter calibration, (3) the exchange of know-how with the partnering organizations, (4) recruitment of senior and junior researchers, (5) increase its participation in European research projects and international scientific teams, and (6) enhancement the transition from research to regional social and economic sustainable development.
After the completion of this Project, the methodology and facilities at the Gavdos and Crete for the calibration of satellite altimeters have improved and were made capable to be extended for other international altimetric satellites using alternative and independent techniques, but also newly developed instruments. Collaboration with all partnering organizations that took place during this reporting period have resulted in long-term associations by signing 3 Memorandum of Understandings with the Austrian, German and French Partnering Institutes.
GeoMatLab has built and established its caliber and capacity within the international community and research teams for satellite calibration and deformation monitoring. It also enhanced its research potential and visibility. The dedicated Gavdos and Crete Cal/Val facilities have established as one of the four international satellite calibration sites in the world. Such stature is earmarked by including the Gavdos Cal/Val facility in the presentation, for the dedicated Cal/Val sites in the world, to be given at the 20 years of progress in Radar Altimetry Symposium, in Venice, Italy, 24-29 September, 2012. The established dedicated Cal/Val site is now fully instrumented to provide an independent (in-situ) determination of sea-surface observations and provide the basis for calibrating the altimetric measurements made by the satellites as they overfly the location. It will provide fundamental calibration information in the centre of the East Mediterranean for an uninterrupted monitoring of the Jason satellite and its successors, as well as the European Cryosat-2, and Sentinel-3 and Chinese and French/Indian missions. Also, the established permanent GNSS network in west Crete and Gavdos is able to monitor crustal deformation in one of the most seismic active regions in Europe on a continuous basis and provide valuable information for earthquake research and interpretation. This site has become essential infrastructure in monitoring sea level variations and climate changes for our planet.
Negotiations with the satellite operators, such as ESA, are under way for funding the establishment of a permanent calibration site for Sentinel-3 in the south west of Crete using the developed transponder. A site with a triple cross over of the Jason, Sentinel-3A & 3B and AltiKa satellites over west Crete has already been identified, tested, and selected. In the same token, a permanent site at CRS1 in southwest Crete is planned for the calibration of the Chinese satellite altimeter.
The Project has also contributed to regional development by unveiling a problem in land subsidence of 2cm/year caused by excessive pumping of groundwater for irrigation in East Crete and by discovering a power-law, and long-range correlation in the observed deformation signals of two GNSS sites. This may have an impact on earthquake research for the region. Finally, local engineers are also using the precise positioning data provided by the established west Crete network of permanent GNSS sites to improve their accuracy and operations cost.
Potential Impact:
Potential impact, main dissemination activities and the exploitation of results (max 10 pages)
1. Potential Impact
Coastal zones in Europe contain large human populations and significant socio-economic activities. They also support diverse ecosystems that provide important habitats and sources of food. One-third of the European Union population is estimated to live within 50 km of the coast, and some 140 000 km2 of land is currently within 1-m of sea level. Significantly inhabited coastal areas in countries such as the Netherlands, England, Denmark, Germany and Italy are already below normal high-tide levels, and more extensive areas are prone to flooding from storm surges. Climate change is an additional pressure and is likely to have significant impacts on coastal zones, particularly via sea-level rise and changes in the frequency and/or intensity of extreme weather events, such as storms and associated surges.
Direct impacts from sea-level rise include inundation and displacement of wetlands and lowlands, coastal erosion, increased storm flooding and damage, increased salinity in estuaries and coastal aquifers, and rising coastal water tables and impeded drainage. Potential indirect impacts include changes in the distribution of bottom sediments, changes in the functions of coastal ecosystems and impacts on human activities.
There are emerging estimates of the physical impacts and economic costs to coasts in Europe from sea level rise and flooding from storm events. Impact results using the DIVA database and models produced from the DINAS-COASTS DG research project (DINAS-COAST Consortium, 2006; Hinkel and Klein, 2007; Nicholls et al., 2007a; Vafeidis et al., 2004; 2007) have been developed for Europe in the PESETA project (Richards and Nicholls, 2007). They show impacts increasing dramatically without adaptation: in the 2080s under the A2 SRES scenario (sea level wil rise 0.23m-0.51m at 2090-2099 relative to 1980-1999) some 19 000 km2 of land in Europe could be permanently lost, potentially affecting some 1.4 million people in Europe experiencing flooding each year, and with an estimated economic costs of 18 billion euro/year .
The most threatened coastal environments within Europe are deltas, low-lying coastal plains, islands and barrier islands, beaches, coastal wetlands, and estuaries. Tidal range is a key factor: in general, the smaller the tidal range, the greater the susceptibility to a given rise in sea level. The Mediterranean and Baltic coasts have a low tidal range (<1 m), which suggests that they will be more vulnerable to sea-level rise than the Atlantic Ocean and North Sea coasts (Nicholls and Mimura, 1998). Habitats could be severely reduced or even disappear during the 21st century because of the low tidal range in these areas and the limited scope for onshore migration, which is due to the intense human use of the coastal zone (Nicholls and Klein, 2003a; Alcamo et al. 2007).
The ocean response to global warming with a sea-level rise, amounting to [+3mm/yr] at present, and the ice melting has been possible to be measured accurately, and unequivocally by satellite altimeters all over the world. Here, an orbiting satellite emits electromagnetic waves to the surface of the Earth. It then records the reflected signals and their time of arrival. From these altimetric measurements, the range from the satellite to the sea and/or water surface can be determined precisely and with respect to the centre of mass of the earth.
Altimeter data have assisted in monitoring sea level changes world wide, but also in forecasting high seas, and in improving operational oceanography (forecasting eddies, etc.) as well as monitoring basin-scale variability in the oceans. Moreover, ocean surface topography with altimetry provides data for operational forecasts ranging from tides and marine ecosystems to human health and safety.
The expected operational time of altimetric missions is however limited; for example it does not commonly exceed 5 years (i.e. ERS-1 from July 1991 to June 1996). Also, the results from each altimetry mission, such as sea-surface heights and sea-anomaly fields, need to be continuously and independently connected onto a common and global reference system. Thus, to observe long-term trends in ocean changes and to distinguish patterns of natural variability, satellite measurements have to be calibrated and validated. Calibration and validation (Cal/Val) of altimetric missions is the process of quantitatively defining and comparing the altimetric systems measurements against well understood and accurately determined in-situ measurements that are independent from the altimeter. The possible altimeter sources of error including the sea state bias, wet tropospheric path delay, marine geoid, tides, and geographically correlated errors are also determined through satellite altimetry calibration.
Calibration is primarily provided by permanent calibration facilities (Cal/Val sites), or by a network of globally distributed tide gauges. Each calibration method presents advantages and disadvantages. For example, permanent Cal/Val sites provide absolute altimeter biases as well as cross-calibration among different satellites, while distributed tide-gauge networks result only in relative bias determination among missions.
The absolute bias of satellite altimetry measurements is, more often than not, determined by permanent calibration facilities (Cal/Val sites) established at dedicated sites all over the globe. In the world, there exist four permanent Cal/Val facilities. Two of those sites are located in Europe (Gavdos in Greece operated by the Technical University of Crete and Corsica in France operated by OCA/CNES), one installed in the USA (Harvest Oil Platform Experiment, California, operated by JPL/CalTech, USA) and the last one set up in Australia (Bass Strait, Tasmania, operated by the University of Tasmania). This SOFIA Project has contributed into the infrastructure enhancement of this Gavdos Cal/Val site.
Current and future altimetric missions (i.e. Cryosat-2, Sentinel-3, etc.) seem to extend the usage of altimetric products to new applications by incorporating novel measuring techniques (i.e. Delay Doppler, wide swath) and unique sensors (i.e. Ocean Land Colour Instrument in Sentinel-3 of ESA). Thus, satellite altimetry is also considered to be an essential tool for estimating river discharges, surface water extent, height and slope, volume change in lakes, flood forecasting and fresh water detection.
Regional and local sea-level rise in Europe generally will differ from the global average because, for example, of vertical land movements (glacial isostatic rebound, tectonic activity, and subsidence). Deviations will also occur as a result of local oceanic effects, such as changes in oceanic circulation, water density, or wind and pressure patterns. Hence, the geographical distribution of satellite altimeter errors must be known. This knowledge is what the proposed project enables with the combined observation of vertical land movements (GNSS data interpretation) and sea level monitoring (tide gauge data).
Upon the completion of the SOFIA project, GeoMatLab has been able to provide calibrated and validated data, information and knowledge to better understand, and assess the Earth, its sea level and its climate.
Social impacts of the SOFIA project are important in the sense that GeoMatLab takes steps in the right direction to understand the geodynamic phenomena associated with the active earthquake zone, providing improved knowledge, which eventually could provide earthquake risk mitigation for the society.
The establishment of a permanent continuously operating tracking network acts as a catalyst in determining the requirements and technical specifications for the recording of multi-disciplinary geo-information. The real-time detection of land deformation changes will especially contribute to understanding the earthquake mechanisms in the area and the relevant crustal motions in a continuous fashion.
The social benefits will be the stimulation of geodynamic and geotectonic research from the point of view of economic and social cohesion, and last but not least, the stimulation of development of a data base with geodynamic, sea level change, geodetic and seismic measurements which will be the basis for future researches in the area.
Another important task of the SOFIA support action is its multi-disciplinary geo-informatic approach at an active geotectonic area. This particular character of the joint program allows the modelling of the dynamics of the area under study and therefore will help in reducing the seismic hazard, contributing subsequently significant social and economic benefits.
2. Synergy with Cohesion Funds
On 5 November 2007, the European Commission approved the Operational Programme Crete and the Aegean Islands. It involves Community support for 3 NUTS II regions of the Greek Islands: Crete, the North Aegean islands, and the South Aegean islands. The three regions covered by the Operational Programme have a rich environment, the potential to generate income from high-quality tourism, important international infrastructure connections (particularly for sea transport), diversified tourist assets as well as some distinguished research centres and universities. Apart from the South Aegean region, however, regional GDP per capita and employment rates are below the national average.
The major financial public investment efforts undertaken in 2007-13 are aiming to:
diversify the economic base of the tourism sector into higher-quality market segments and innovative approaches;
provide enhanced infrastructures to improve accessibility;
promote sustainable development through increased emphasis on the environmental dimension of all actions;
provide environmental infrastructures, nature protection and the proper management of natural resources;
utilise the natural and cultural heritage within the context of sustainable growth;
promote digital convergence and entrepreneurship;
combat intraregional disparities, notably in the South Aegean region.
Along these lines, the SOFIA Project activities rhyme along to:
provide environmental infrastructures (i.e. the scientific equipment installed in Gavdos and western Crete to calibrate satellite altimeter and monitoring crustal deformation);
promote digital convergence and entrepreneurship (priority axis 4) through the improvement of the Technical University of Crete infrastructure and development of innovate products (i.e. the development of a prototype instrument for the calibration of Cryosat-2 and Sentinel-3 altimeters);
contribute to sustainable development and quality of life (priority axis 7) through the protection of environment (monitoring of environmental parameters related to earthquake risk prevention and tsunamis warnings);
contribute to the goal of income generation through exploitation of its results for high-quality tourist, archeological and surveying applications in Crete;
creation of two new jobs, conservation of other four and creating the conditions for recruitment of more researchers;
improve of the scientific excellence of the region (according to the Innovation Scoreboard 2006 methodology Region of Crete takes the 174th place of a total of 203 EU-25 regions)
improve participation of the Technical University of Crete in RTD projects (TUC participated in 12 RTD projects financed from the Operation Programme Competitiveness 2000-2006; Source General Secretariat of Research and Technology).
It is clear that the activities that have been implemented through SOFIA project are in line with the European funding directions, like ERDF and the Cohesion Fund, and the Operational Programme Crete and the Aegean Islands.
3. Dissemination Activities
A Technical Workshop on Satellite Altimetry Calibration & Deformation Monitoring with GNSS has been organised by GeoMatLab on 20-21 January 2011. The workshop took place at the Center of Mediterranean Architecture, Old Venetian Harbor, Chania, Crete, Greece. Invitations for participation have been sent to top-class researchers. Representatives from all partnering organizations participated in this meeting. Conclusions and Recommendations drawn from the Crete Workshop in Chania, 20-21/Jan/2011, have been as follows:
1. All satellite calibration/validation world sites should aim at two objectives: a) To report on the satellite altimeter bias and their byproducts, as users will directly apply these to get unbiased altimetry products; b) to try new corrections-algorithms to improve future altimetry products and provide more insight into the origin of errors and biases.
2. All satellite altimeter Cal/Val sites in the world (Corsica-France, Gavdos-Greece, Harvest-USA, Bass Strait-Australia) should make an effort to homogenize solutions and results. Homogenisation may entail the following actions: a) All Cal/Val sites should apply common processing strategies and loading models (tides, atmosphere etc,) for their GNSS data to produce comparable results in a common world reference system using the same world GNSS/IGS reference sites; b) The coordinates and velocities of their Cal/Val reference sites should be tied to the same global frame (i.e. center of mass of the earth); c) GLONASS measurements as well as GPS data is recommended to be used in their GPS reference site solutions; d) Different software, such as Bernese, GIPSY, GAMIT should be applied for precise positioning solutions of the reference sites; e) For the ionosphere corrections, GDR dual ionospheric corrections should be used, instead of GPS ionosphere modelling; f) The wet troposphere corrections, based on local GPS, should serve for comparison and to cross-validate satellite results. Radiometer corrections used over the whole ocean must be used for continuity. Investigations using local GPS give insight on the error budget in coastal areas. Development of new algorithms (e.g. S. Brown) and/or new instruments is strongly encouraged to avoid land contamination; g) Retracking is also an important issue when satellites are approaching the coasts and should be applied; i) Looking at 18/20 Hz to assess quality of waveforms (that can impact estimates of ranges); j) Open ocean SSB models are not valid in coastal regions. The SSB correction may require further investigation, for example development of local models, use of instruments to measure wave, swell, new parameterisations to capture increased non-linearity of waves, etc. The SSB is intimately linked to waveform retracking, e.g. coastal wind sheltering will cause specular waveforms that affect retracking performance; k) Cal/val can benefit of advances in coastal altimetry, especially exploiting coastal-GDRs (from PISTACH, COASTALT, CTOH initiatives).
3. When calibrating satellite radar altimeters with GPS buoys, then: a) GPS heights should be determined with the antenna radome on and off to determine biases in heights and systematic errors before deploying the buoy on the sea surface. These tests can be conducted on ground for long period (at least 1 day); b) In a GPS-buoy campaign, accelerometers may be installed to determine the significant wave heights and thus the sea-state bias; the SWH can be also determined by the raw movement of the buoy after applying a low-pass filtered time series.
4. Atmospheric loading effects are of the order of sub-cm;
5. Geoid heights and local measuring conditions may be shared by all Cal/Val sites;
6. Digital Elevation Models are useful to have in altimetry calibration. Phillipa Berry may help in that direction for ACE2 and details.
7. TIGA processing and analysis should be re-activated and all Cal/Val sites should be re-processed.
8. The IGS does not maintain a public archive for all GNSS sites. More precise positioning solutions are required by the Cal/Val sites.
9. Transponder calibration algorithms and procedures should be investigated for the new altimetric missions as well.
Participants from Australia, Germany, France, Hungary, Italy, Greece, Denmark, etc. took place in this International Workshop.
A Regional Outreach Workshop on "GeoMatLab's contribution to local and regional capacity building" has been organized by the Geodesy & Geomatics Engineering Lab of the Technical University of Crete. This Workshop took place in the city of Chania, Crete, Greece, on 1st July 2011.
The purpose of this Regional Outreach Workshop was to inform local, regional and national authorities for the results obtained so far by the REGPOT project SOFIA and the way that these results might be further exploited to contribute to regional sustainable development. Top scientists and stakeholders have been invited to participate in this Outreach Workshop. Also, there was a Session dedicated to the presentation of upcoming Call for Proposals under the framework of the "Regions of Knowledge", "Research Potential" and "Ideas" programs. A round table discussion for better exploitation of Structural Funds for Research and Technological Development also took place.
Besides the organization of these workshops dissemination of the SOFIA project has been acquired through the establishment of the projects website (http://www.geomatlab.tuc.gr/lab-projects/sofia) participation of GeoMatLab personnel in international conferences and workshops while dissemination of SOFIA project results to the general public has been performed via interviews and article publications in regional and national mass media.
10. Exploitation of SOFIA project results
The significant improvement of GeoMatLabs visibility at the international scientific community has been realised through the previously mentioned dissemination activities as well as the publication of several peer-reviewed articles in scientific and conference proceedings. The research quality of these publications as well as the attendance of GeoMatLabs in a number of international conferences were the main reasons why international organisations and stakeholders (besides the SOFIA partnering organizations) expressed their interest in collaborating with GeoMatLab (i.e. India and China).
More specifically, negotiations with the satellite operators, such as ESA, are under way for funding the establishment of a permanent calibration site for Sentinel-3 in the south west of Crete using the developed transponder. A site with a triple cross over of the Jason, Sentinel-3A & 3B and AltiKa satellites over west Crete has already been identified, tested, and selected. These initiatives have been formally announced by ESA.
In the same token, a permanent site at CRS1 in southwest Crete has been set and planned for the calibration of the Chinese HY-2 satellite altimeter and collaboration with the First Institute of Oceanography, State Oceanic Administration, China. This collaboration will be further enhanced through the FP7-PIRSES-GA-2012-318950 project entitled: CALT: A global network of permanent sites for calibrating satellite altimetry missions coordinated by GeoMatLab. The French Partnering Organization, OCA, as well as the University of Amazon, Brazil also participate in this project. It will start on October 2012. GeoMatLabs collaboration with the Chinese altimetric community will be further enhanced if the proposal submitted under the framework of a bilateral Greece-China Call, entitled: SPARKLE: Innovative Technologies for Calibrating Satellite Altimeters using prototype instruments of microwave transponders and integrated GNSS buoys is selected to be founded (evaluation results are pending).
The work conducted for abrupt change detection and deformation monitoring will be further exploited, because the developed algorithms will be implemented for the identification of landslides in highways under the framework of the project ISTRIA: Development of an Integrated System for Rockfall Identification in highways that was recently (August 2012) approved for funding from the Greek General Secretariat for Research and Technology. The precise positioning data provided by the established GNSS TUC-net array is being used by local engineers to improve their accuracy and operations cost. Finally, the establishment of the first Greek EGNOS station as well as the first European BeiDou/Compass receiver inside the University Campus will further promote GeoMatLabs research capacity and contribution to regional development providing that, especially, EGNOS has numerous application directly related with societal needs like navigation of vehicles, aircrafts and ships and with search-and-rescue applications.
Finally exploitation of SOFIA project results is expected to occur through the collaboration that GeoMatLab has initiated with public (i.e. Greek Cadastre, Region of Crete) and private (i.e. PRISMA Electronics, General Consulting ISTRIA SA, AGA Hellas) entities.
List of Websites:
http://www.geomatlab.tuc.gr/lab-projects/sofia
