A.G.A. van der Hoeven and R F Hanssen

Cross-validation of tropospheric water vapor measurements by GPS and SAR interferometry

In: General Assembly European Geophysical Society,
The Hague, The Netherlands, 19-23 April 1999, 1999.

Mesoscale tropospheric water vapor distribution is a key parameter in meteorology and atmospheric science. As water vapor content is highly variable both spatially and temporally, it is difficult to measure and model accurately with conventional methods.

For point positioning techniques such as GPS and InSAR, water vapor causes an additional delay of the signal. The variability of water vapor content can therefore result in systematic errors, mainly in the vertical component.
A study is performed to investigate the possibility of combining measurements of GPS and interferometric SAR for cross-validation of observed water vapor content. This approach can also be used to improve the positioning accuracy of both techniques. For this study, interferometric radar data acquired over the Netherlands during the ERS-1/ERS-2 tandem mission (1996/97) are used. A comparison with continuous GPS measurements from the Dutch GPS network is performed. GPS water vapor estimations are generated using an SRIF filter algorithm while solving for the satellite and station positions, satellite clocks and zenith delays. SAR water vapor estimations are derived from 1-day interval interferometric pairs. The interferometric images are unwrapped and a digital elevation model is used to eliminate topographic influences to enable the retrieval of delays caused by atmospheric water vapor.