Comparative Experiments on Soil Moisture Monitoring with GPS SNR Observations

Using the SNR observations from geodetic UPS receiver to monitoring the soil moisture is a new method，which does not suffer from destruction of observed soils，difficult data assimilation and time-spatial resolution limits. However，there are issues need to be solved such as uncertain measuring area，selection rules of parameter as wavelength and satellites，and construction of relationshipmodel between the relative delay phase and soil water content. To solve these problems，the Fresnel zone theory is introduced，and two comparative experiments based on simulated and measured soil moisture are carried out. The process and results of experiments show that the remarkable correlation，which can be described well by exponential function，does exist between the relative delay phase and soil moisture. The maximal effective monitoring distance is within about 45 meters. Meanwhile，selection of an advanced satellites and recording of L2C can increasingly improve the quality of SNR and lead to more reliable results.