Measurement of height and moisture of an agricultural vegetation using GPS/GLONASS receiver

In this paper, possibility of measuring of moisture and heights of vegetation at agricultural fields using receiver of global navigation satellite systems (GNSS) signals is theoretically and experimentally studied. Measurement of GNSS interference pattern (interferogram) was held in August 2013 at suburb of Krasnoyarsk on agricultural fields planted with rape, rye, wheat and barley. Signals of GLONASS and GPS were recorded on a standard receiver MRK-32P (“Radiosvayz”, Krasnoyarsk). Measurements of texture, bulk density and volumetric moisture of soil at the depth of 5 cm and 10 cm, height, volumetric moisture and bulk density of the vegetation were carried out synchronously with the measurement of interferograms. In addition, the dielectric measurements of rye were carried out based on which dielectric model was built, that is allowed to calculate the complex permittivity of vegetation, depending on its volumetric moisture content. The method of retrieving of volumetric moisture and heights of vegetation is based on solving the inverse problem by minimizing the norm of the residual between the measured and theoretically calculated interferogram. The theoretical model of interferogram takes into account only the coherent component of field of reflected wave from the rough soil surface covered with a vegetation. At the same time, the volumetric moisture and texture of soil were assumed as known parameters. As a result, a good agreement between measured and calculated interferograms was shown. Retrieved vegetation heights and moisture on the test plots with an average error of 0.17 m and 0.21 kg/m 2 corresponds to values, which are measured by the contact method.