Wondering if it’s preferable to have a smaller temporal difference but a larger perpendicular difference or an image with a larger temporal diff. but a smaller perpendicular diff. to obtain the best coherence. Or do they affect the coherence equally?
The best slaves for my master image are either an image with -20m, -24 days or -88m, -12 days compared to the master.
That also depends on if want to extract a DEM or deformation.
For Sentinel-1, temporal decorrelation has usually the higher impact so I would always recommend the smaller temporal difference (unless you are not working in desert regions). Besides that, a perpendicular baseline of 20m is very small, so i would go for 88m and 12 days.
Have a look at these ESA notes on the selection of suitable images: http://www.esa.int/esapub/tm/tm19/TM-19_ptB.pdf (chapter 1.3 )
Thank you for the link!
Is the reason to always use small temporal differences in desert regions due to aeolian processes having a larger affect on the surface there?
Depends on the desert. if the desert is very dry (with lots of penetration), a short baseline might be preferable due to smaller amount of volume scattering. On the other hand wind-deposited sand can kill coherence if the temporal baseline is too long.