Algorithms for calculation of digital surface models from the unwrapped interferometric phase

The focus of this paper is on interferometric DEM generation algorithms from imaging geometry analysis. The proper description of the interferometric imaging geometry is presented. As a result of solving the two sets of range-Doppler equations one also obtains the interferometric alongtrack baseline component. This fixes the imaging positions of each pixel in the case of known antenna tracks. Conversely, if the relative positions of the antenna tracks are not precisely known, one may adjust the interferometric baseline by comparing the azimuth-offsets from image correlation to the calculated alongtrack baseline. As an example, the angle of convergence is estimated using single-pass interferometric DOSAR data motion compensated to individual reference tracks. A new method of estimating the absolute phase difference is suggested which exploits the range-offsets obtained from correlating the complex image pair. Finally, it is shown that layover produces a residual tilt in interferometric DEMs if the crosstrack-coordinate is left unfiltered