Relation of dielectric with the soil moisture on SAR image

I have read threads related to finding soil moisture using S1A imagery but I am new to the relation of backscatter with soil moisture.
the water appears black due to specular scattering but I wanted to know two concepts.

  1. Moist soil means more dielectric ( since water has high dielectric, right?), so the moist soil will look darker(since water looks dark in SAR images) or wet soil will look bright than dry soil having the same roughness? If wet soil will look bright, please let me know why?

  2. If two scenes have the same soil moisture but Image A has more roughness than Image B. Which will look brighter or how to differentiate?

I will be very grateful to anyone giving me clarity over this. I have tried reading online but couldn’t gain useful insight. This community is my go-to place for any SAR-related doubts in general.

We have to separate these two:

  1. Open water bodies: Specular reflection, the more smooth the water the lower the backscatter intensity, the darker the image.
  2. Water in volumes (soil, plants, ice): Here the high dielectricity causes higher backscatter with increased water content.

The separation of roughness and moisture can not be done for a single image, the return is ambiguous. Polarimetric approaches try to decompose the returning signal into contributions of different scattering mechanisms (surface, dihedral, volume) or components (roughness, moisture, shape).

1 Like