Soil Moisture Radar
From Agrineer.org Wiki
The Soil Moisture Radar project implements a Software Defined Radio (SDR) bi-static radar, using GPS signals, to estimate soil moisture. GPS signals are ubiquitous and suited for top layer soil penetration. The difference between a signal that has reflected through the soil and one that has not gives an indicator of soil moisture. The signals to compare are derived from one antenna pointing up (direct and normal usage) with an antenna pointing down receiving the reflected signal.
This project is under development.