SURVEY OF RADIO FREQUENCY TECHNIQUES FOR TELEDETECTION OF SOIL MOISTURE.

The paper outlines the principles of operation of contact and noncontact methods as well as recent developments in radio frequency techniques for detection of soil moisture content. In the case of noncontact techniques, emphasis is placed on the interaction between measurement quantities which introduces ambiguities and limits the skin depth and overall progress in this area. Attention is also focused on the effectiveness of contact methods employing immersion-type sensors operating in the time or frequency domain, as well as the potential of hybrid techniques employing beacons interrogated by remote sensors during data reconnaissance missions.