Ground-to-volume scattering ratio

How can I find the ground-to-volume scattering ratio for vegetation density estimation? can anybody please tell me.

Please have a look at this thread,

Source of the thread

And also the following could be good start,

On the Separation of Ground and Volume Scattering Using Multibaseline SAR Data

Source: https://ieeexplore.ieee.org/document/7997694

Thank you for the links. They were helpful!