They amount about 100m to 800m. Of course, the approriate baselines will be smaller, if the the temporal decorrelation is great. They have the best coherence and DEM accuracy. The decorrelation theory failed, if the SAR targets are corner reflectors. For small acquisition time interval and baselines smaller than the critical baseline, rural areas have better coherence than cities.
Forest has always the worst coherence among the three land covers.
Baselines more than 1000m will make the coherence of general land covers nearly uncorrelated. The authors would like to thank the European Space Agency, who have provided the ERS-1 SLC data. 33, No. 20, July 1994, pp.4361-4368. Remote Sens., vol. Remote Sens., vol.