Coherence estimation (InSAR operator)

Coherence estimation

This operator computes/estimates the coherence image, with or without subtraction of the reference phase. The reference phase is subtracted if there is a 2d-polynomial computed -- result of "Compute Interferogram" operator. While, it is not subtracted if this information is not in the metadata, or if the number of polynomial coefficients in "Compute Interferogram" operator is set to 0.

Note that this is a "general" coherence estimation operator and not exclusive only for InSAR applications. It can be utilized to estimate the coherence information from any stack of coregistered complex images.

In order to reduce the noise, as the post-processing step, you can perform multilooking (with Multilook Operator). In case of ESA's ERS and Envisat sensors, the factor 5:1 (azimuth:range) or similar ratio between the factors is chosen to obtain approximately square pixels (20x20 m^2 for factors 5 and 1). Of course the resolution decreases if multilooking is applied.

Operator parameters:

  

The input parameters are size of the shifting window for the coherence estimation. The window size is defined, in both azimuth and range directions.

Source bands:

  

Source Bands are set of, usually coregistered, bands of the complex product.