Comments: We start with a short overview over the information content of convential SAR images. Very much simplified, the SAR imaging process works like this: The sensor emits a microwave pulse to the ground, the wave travels to the ground, is scattered there, travels back to the sensor and is finally received there. The received amplitude depends of course on the power of the sensor and on the distance to the objects. But the most interesting parameter for conventional SAR imaging of course the scene reflectivity.

The scene reflectivity is generally a complex. Every individual scatterer in the resolution cell reflects the wave, and the received wavefront is a coherent overlay of all the individual waves. Due to the coherent nature of SAR sensors, the observed amplitudes can vary very strongly even for homogenous areas, as the amplitude of the coherent sum of all contributions can be regarded as the result of a random process (speckle phenomena). Typically for a homogenous area is only the average backscattered power, but an individual pixel of it can show a very different value.