Tide gauge measurements and satellite radar altimetry are the primary methods to study sea level variations. Analysis of tide gauge measurements with the purpose of sea level change research requires a well defined vertical reference to separate apparent sea level changes from climate induced. Such a reference frame can be realized through precise positions of Global Navigation Satellite System (GNSS) stations located at or near tide gauges. Establishing such reference frame is one of the purposes of the GPS Tide Gauge Benchmark Monitoring Pilot Project
of the International GNSS Service (
). The required accuracies are about 5-10 mm for station positions and less than 1 mm/year for vertical motions.
Presently six TIGA Analysis Centres (TAC) contribute to the project, namely, a consortium of University of Canberra, University of Tasmania, and Australian National University, German Research Centre for Geosciences (GFZ) and University La Rochelle (ULR, France) processing global station networks as well as Geoscience Australia, German Geodetic Research Institute (DGFI), and EUREF Subcommission through Federal Agency for Cartography and Geodesy (Germany) processing regional station networks. The latest solutions derived at the TACs using absolute model for antenna phase centre variations and other models are available at TIGA archive via anonymous ftp.
GPS data from about 400 GPS stations globally distributed (Figure 1) were recently processed at GFZ TIGA analysis centre using EPOS-Potsdam software (version 7) covering the time span from January 4, 1998 till December 29, 2007 using consistent models. Weekly coordinates of GPS stations, daily values of the Earth Rotation Parameters (x and y pole coordinates and their rates, Length of Day) as well as satellite antenna offsets are available in SINEX files /wWWWW/gftWWWW7.snx.Z at TIGA archive, where WWWW stands for GPS week in the range from 0939 till 1459.