Backscatter Coefficient
What is considered to be clutter by one user may be a target for another. Usually targets may be considered to be a point scatterer and clutter as extended, covering many range, angle and Doppler cells. The clutter may fill a volume (rain) or be confined to a surface (land). In principle all that is required to estimate the return (backscatter) is a knowledge of the volume or surface illuminated and the echo per unit volume, η, or per unit surface area, σ°, (the backscatter coefficient).
Read more about this topic: Clutter (radar)