GAMMA Questions

Hi everyone

I've noticed when creating interferograms from CSK data that specifying different range and azimuth positions for offset estimation when using the init_offset_orbit and init_offset commands results in different interferogram scenes (geocoded size and geographic extent).
I tested three different sets of values (rpos/azpos):
1) 2000/2000
2) 2000/20000
3) default scene centre of SLC

The results (see attached images) are that options 1) and 2) look similar visually, but have slightly different geocoded sizes and geocoded extent. Option 2) and 3) do not have the same extent visually according to the MLI, but have the same geocoded size and geocoded extent. Option 3) also has the issue of sometimes very low coherence for several interferograms that have good coherence when using either option 1/2. The MLIs were processed at 10 10.

My understanding was that regardless of what rpos/azpos you choose, this should not affect the resulting size and geographic extent of the geocoded output interferograms. However this does not appear to be the case.
I was wondering why these different options result in different size and geographic extents (or in the case of option 2 and 3, the same size and extent but lack of coherence), and how one can determine which value is best to use for your dataset?

Thanks in advance,
Kirsten