Surface radars emit waves that refract off the ground or sea, and are reflected not only by Objects of Interest (flying objects, ships, vehicles), but also by a large amount of noise and clutter (land features, buildings, vegetation, etc.) or sea (waves, spray, etc.).
This land or sea clutter, as well as the low speed of movement of surface radars, distinguishes them from airborne or spaceborne radars.
As a result, different design choices are required, even though the following basic principles are the same: