Subsidence map in 3d view

Microwave Toolbox
2

the unwrapped phase is the change of surface elevation in the looking direction of the SAR wave.

Try
Radar > Interferometric > Products > Phase To Displacement
This should actually convert it into measurable units.

However, I wasn’t lucky with it so far and used another approach in band maths:

  1. (Unw_Phase * wavelength in mm) / (-4 * PI * cos(rad(incident_angle)))
    This gives you the relative change between two satellite images in milimeters
    Source: http://www.esa.int/esapub/tm/tm19/TM-19_ptA.pdf, chapter 2.3.

  2. Crop out areas with a low coherence (Layer properties > valid pixel expression, for example coh_HH_11Feb2008_04Mar2008 > 0.6).

  3. Select a point where you assume no change and read the value. Let’s say its 45 cm

  4. Subtract 45 from your image in order to have zero values at those areas with no change. The remaining variation should be due to subsidence between two overpasses.

10 Likes