ESA
The Interferometric Coherence product is the amplitude of the complex correlation coefficient between two images. In simple way, coherence describes similarity between two images in a range between zero to one. Zero means pixels were totally different where one means pixels were same exactly.The product algorithm starts from two ESA Level-1 SLC products which are from the same area, the same relative orbit number and preferably from within a short time interval (6 days is the shortest possible with S1A and S1B pairs). The original paired images go through a workflow of orbit correction, co-registration through back-geocoding, coherence calculation and terrain correction by making use of standard SNAP tools as part of the Sentinel-1 toolbox (S1TBX).The terrain correction step is intended to compensate for distortions due to topographical variations of the scene and the tilt of the satellite sensor, so that the geometric representation of the image will be as close as possible to the real world.
Sentinel-1 Level-1 Single Look Complex (SLC) Coherence products 2015-11