Interferogram production procedure
Radar Interferometry

Before any interferogram can be produced, the radar images to be combined must be synthesized. Any differences introduced into this synthesis will be detrimental to the quality of the result. It's important to avoid introducing any spurious phases: remember that conventional image processing neglects phase, and that spurious phases have no effect on image processing. Similarly, the filters used, which control the weighting of elementary targets on pixels, should if possible be chosen identically for each image, as should the choice of processing Doppler, even if the optimal Doppler is not the same for each image. As a joke, it's much better to treat both images equally badly than to treat them optimally, but differently.