David T. Sandwell and Evelyn Price, Institute of Geophysics and Planetary Physics,
Revised June 30, 1997
We demonstrate the method by averaging/differencing 6 interferograms, having a suite of perpendicular baselines ranging from 18 to 406 m. Cross spectral analysis of the difference between two tandem interferograms provides estimates of spatial resolution which are used to design pre-stack filters. A wide range of perpendicular baselines provides the best topographic recovery in terms of accuracy and coverage. Outside of mountainous areas, the topography has a relative accuracy of better than 2 m. Residual interferograms (single interferogram - stack) have tilts across the unwrapped phase that are typically 50 mm in both range and azimuth reflecting both orbit error and atmospheric delay. Smaller scale atmospheric waves with amplitudes of 15 mm are interpreted as atmospheric lee waves. A few GPS control points within a frame could increase the precision to about 20 mm for a single interferogram; further improvements may be achieved by stacking residual interferograms.