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.
Abstract:
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.