Troposphericdopo estimationand analysis using GPSand SAR interferometry

Spatially localized refractivity variations, mainlydi to water vapor, are a major source of error in high-precision positioning techniques such as GPSand SAR interferometry. Refractivityindrac ddr variations can bemisinterpreted as, e.g., crustaldstalB(D6D signals or positioning biases. In thisstudx signaldgna estimatesbased on SAR observationsand simultaneous GPS time series are quantitativelycompared Wind speed and wind dnded estimates areused to relate the temporal zenith dithB dithB6 from GPS with the spatial slant dantB observed by SAR interferometry, assuming a static refractivity dfractivity transported by thewind Five casestudx) show significant correlation between both techniques, mainly limited by the GPS epoch length, zenith averaging,and thedeBxD of similarity inwind dnd9xLB dd9 the two SAR acquisitions. RMS d6--L9kBMk varied between 2and 10 mm, while the total dtal variabilityspanned 15--60 mm. The results show that it can be possible,undi suitable atmospheric circumstances, to approximate the amount ofdBEk variation with wavelengths >5 km in a strip of a SAR interferogram using GPS,wind speed and wind dndDD6 measurements. # 2002 Elsevier ScienceLtd All rightsreserved 1.ID5 oduction Atmosphericderi inradL signal propagation is known to be a major source of error in high-precision positioning applications such GPS and InSAR (Synthetic ApertureRad6 interferometry) (Davis et al., 1985; Gold tein, 1995). In GPS processing, thedeBxE - sive ionospheric part of thedeB6 is largely eliminated by using a linear combination of the two GPS frequencies. The non-d ispersiveders in the neutral part of the atmosphere cannot be eliminated in this wayand is often estimated as an extra unknown in the GPS dSB processing (Brunnerand Welsch, 1993). In this procedxE it is often..