Change detection

As a predictor:

InSAR coherence analysis predicts the quality of the monitoring product. Such an analysis is useful before engaging into a log term monitoring project and it is recommended to be carried on in any area that wasn’t previously monitored with InSAR.

A good quality displacement monitoring product is expected for yellow and red areas in the illustrated coherence map. This is because in those areas the radar signal didn’t change within the period of measurement, thus the information that it carries (displacement in particular) is still intact.

As a detector:

The gain/loss of coherence in a specific area is the result of specific changes on the ground. By knowing the types of activities and events that happens on a specific area, the dates when these activities occur could be detected from changes in the coherence levels.

As an example, the approximate harvesting dates in an agricultural field can be detected, as illustrated in the figure.