Surface Soil Moisture Estimations Using GPS-Interferometric Reflectometry: Error Sources And Sensing Limits
Chew, Clara 1 ; Small, Eric 2 ; Larson, Kristine 3
1 University of Colorado
2 University of Colorado
3 University of Colorado
GPS-Interferometric Reflectometry (GPS-IR) is a new method of environmental monitoring that relates changes in ground-reflected (multipath) GPS signals to changes in snow depth, surface soil moisture, and vegetative state for an area of approximately 1000 m2 surrounding a GPS antenna. Changes in multipath signals are seen in signal-to-noise ratio (SNR) interferograms, which are recorded by the GPS receiver. Temporal variations in the phase, amplitude, and frequency of SNR data are related to variations in surface permittivity, which is in turn primarily a function of the surface’s water content. Here, we summarize the current soil moisture sensing limit of our technique, using both field data and an electrodynamic model to guide our analysis. Our results show that overlying vegetation is the primary source of error in our soil moisture estimations. However, after accounting for vegetation, the RMSE between our estimates and in situ data is <0.05 cm3 cm-3.