3. Information provided by radar interferometry

Building an interferogram is straightforward and requires no special knowledge, as shown in figure 4 . All known information is gathered, including orbits and any available digital terrain models. For each point in the terrain model, the terrestrial coordinates are calculated using an appropriate geographic subroutine. We then calculate the position of each satellite as it passed closest to the point, using an appropriate orbital subroutine. Finally, the distances between the satellites and the point are calculated, and the difference is calculated. This difference must be doubled to account for the round trip, before being divided by the wavelength. The result of this operation, of which only the non-integer part is kept, is the expected phase cycle fraction. Having identified the corresponding...