Through the phase observations are suggestive of the wide‐area deformation measured, the atmospheric effects are large enough to limit the interpretation of the result. It is difficult to characterize centimeter‐scale deformations spatially distributed over tens of kilometers using differential interferometry without supporting simultaneous, spatially distributed measurements of refractivity along the radar line of sight. So coherence map is just an index but it is not enough.
Different studies imply longer wavelength instruments are more appropriate for studying surfaces by repeat‐pass observations.
the coherence band of interferogram is quality map of two signals aimed by two different (differents positions) antennas and reflected by the seam target, his quality map will be which used to evaluate the reliability of the differential phase reflected.morevere, the coherences bands have used in InSAR time series methods (BASS technique and PS technique )to select PS pixels (persistent scatterers ) which have stable behavior over all time se.we can also use the coherence map to detect the urban damadji causing by naturals or industriels events.