UWB Reflectometric Method for the Measuring of Vegetation Biometric Parameters and Soil Moisture

DOI: 10.1109/USBEREIT58508.2023.10158880

In this article, a method for the simultaneous measurement of total biomass, vegetation water content, and soil moisture is developed based on ultra-wideband (UWB) nadir observation of the reflection coefficient in the frequency range from 450 MHz to 6 GHz. The proposed method is based on a simple model of plane wave reflection from a vegetation layer with flat boundaries lying on a smooth soil surface. The model does not take into account the phenomena of wave scattering on the vegetation elements and the soil surface roughness. The dielectric constant of the vegetation canopy and soil were calculated based on Ulaby and Mironov dielectric models, respectively. The proposed method was tested using data from PORTOS-93 (INRA) experiments on measuring: total biomass (up to 3.3 kg/m2), water content (43%-89%), height (up to 1m) and volumetric content (up to 0.6-0.8%) of wheat plants, moisture (from 5% to 36%), density and clay fraction content (27%) of the soil. As a result, it was shown, the coefficient of determination (R2) and root-mean-square error (RMSE) appeared to be equal to R2=0.999 and RMSE=2.2% when comparing the original and retrieved values of volumetric soil moisture. The retrieved values of total biomass (vegetation water content) with the coefficient of determination R2=0.999 (0.998) and RMSE=16g/m2 (0.7%) coincide with the original set values. Therewith, the bands from 4 GHz to 6 GHz and from 450 MHz to 1 GHz were used to retrieve the canopy biometric parameters and soil moisture, respectively.