GPS

Which GPS stations?

Station active (305) No data for 30 days (66) Decommissioned (67) No observations in SONEL (Survey) = 122 All GPS data available (RF stations included)	Display	Data centres	Programs & Networks
	Active Stations No data for 30 days Decommissioned	BAFG BIGF BKG (EPN, IGS) CDDIS (IGS) CEA CRS ENS GEOLOGIE ESEAS GSA (SPSL) GSI GSN HARTRAO IBGE IGNE IGNF (IGS) IGNF (IGS-MLV) IGNF (RGP) IGNF (RGP-MLV) IGNRA JUSSIEU KASI (IGS) NOAA/NGS/CORS PUERTOS DEL ESTADO RING SEGAL SHOM SIO (IGS) SIRGAS SIRGAS_PUB SOEST-HAWAII SOPAC TUDELFT UJAEN ULR UNAVCO WCDA	AMMA ESEAS EUREF GCOS GNET IGS IGS08-RF PSMSL REFMAR SONEL TIGA
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Survey on Continuous GPS and Tide Gauge co-locations (CGPS@TG)

Survey results table

In order to get a better idea of the status and opportunities on continuous GPS positioning of tide gauges, a survey is carried out periodically within various geoscience communities. The survey aims to identify the existing permanent GPS stations which are close to tide gauges (up to approximately 10-15 km).

Survey form

 The survey results can be viewed in conjunction with SONEL data holdings on the map (above). Purple symbols correspond to stations for which there are no observations in SONEL yet.

 By clicking on the table icon an on-line updated view of the CGPS@TG information that has been supplied to us is displayed. The table can be sorted by clicking on the column items, and a version of the view (table) can be downloaded in a format compatible with applications like excel (.csv).

Survey results on .kmz file

 A ’.kmz’ file provides a Google Earth view of the CGPS@TG geographical distribution. The cgpstg.kmz file is consistent with the above mentionned table (updated weekly). Clicking on a station symbol provides ancillary information on the station, and further clicking on the station name provides access to the so-called GPS sitelog (if the GPS data are available). The CGPS@TG ’kmz’ view might be useful in conjunction with the ’.kmz’ files of satellite radar altimetry ground tracks provided by CLS, or with the ’.kmz’ file of tide gauge records provided by the PSMSL.

 In addition to the periodic surveys, information on CGPS@TG co-locations can also be supplied to us any time by filling in this form. Thank you in advance for your collaboration.

Which GPS data?

The GPS observations that we provide are in the form of daily 30s files (24h of observations at 30s intervals) in the standard international RINEX format. Further information on the RINEX files.

Apart from the RINEX observation files of the GPS stations, SONEL provides ancillary information which enables a precise analysis of the GPS measurements, in particular :
 the precise orbits of IGS,
 the Earth orientation parameters of IGS.

How to get access to the GPS observations

The GPS observations are published on the anonymous FTP server of SONEL. The conditions of access are that the origin of the data is acknowledged in all communications, oral or written. Further details.

The FileZilla tool is a free client ftp which allows you to access the data. Should you have any problems, the following address will enable you to consult the data on the server via a web interface: http://www.sonel.org/ftpWeb/

Which GPS solutions ?

 The processing of GPS observations is particularly complex for the calculation of vertical movements of the land on which the tide gauges are placed (movements of the order of mm/year). The article published in 2007 by the members of the consortium of the ‘ULR’ GPS analysis centre describes the difficulties and the challenges raised by this issue. The figure opposite illustrates the challenges : shown on the left is a series of average sea levels measured with tide gauges ; in the middle the series are corrected with the predictions of the de postglacial rebound model ICE5G (VM2); on the right with the GPS velocities obtained by the ‘ULR’ centre in ITRF2005.

Cluster Ymir (ULR)

 To meet this challenge SONEL relies on the ULR analysis centre whose computation facilitiy is situated at the University of La Rochelle. The cluster acquired in 2008 reduced significantly the calculation time, from 1 year down to 2-3 weeks to process 10 years of GPS observations from a global network of some 200 stations. This has opened up new perspectives of experimentation and important avenues of research (new strategies, modeling, corrections). In particular, it enabled the ULR group to collaborate with 9 of the most prestigious groups in the spatial field in the first reprocessing campaign of the international service IGS.

 The latest ULR solution published in Journal of Geophysical Research is available in SONEL as time series of daily positions and velocities. Click on the link below to obtain more details and retrieve the results.

 The members of the ULR consortium