Microwave Emission Model Parameter Tuning for Surface Soil Moisture Retrieval Using UAV-Mounted Dual Polarization L-Band Radiometer
Abstract
Surface soil moisture retrieval from L-band brightness temperature has been developed for the past decades due to multiple beneficial characteristics of 1-2 GHz frequency bands for remote sensing of the environment. Numerous microwave emission models have been proposed for tower and satellite-based operations with successful retrieval of surface soil moisture and vegetation water content. As a result of the development of cost-effective and low-mass microwave L-band radiometers such as the Portable L-band Radiometer (PoLRa), surface soil moisture surveying traditionally developed by satellite missions SMOS and SMAP can now be developed at local scales, bringing these operations to commercial small unmanned aerial systems (sUAS) providing high detail resolution retrievals at low elevation (7 m or lower depending on canopy height). Due to its cost and limited access, low-altitude, sub-orbital L-band dual polarization radiometry operations for soil moisture retrieval still need further exploration. This study used an sUAS-mounted L-band radiometer and a multispectral camera to model surface soil moisture over irrigated alfalfa cropland in New Mexico’s Rio Grande Valley. This setting allowed varying soil and vegetation moisture conditions, validating with commercial soil moisture probes. This work compared dual and single polarization algorithms using the single scattering Tau-Omega (τ -ω) model with a conventional dielectric mixing scheme, a semi-empirical HQN roughness model and NDVI derived τ to retrieve soil moisture. The calibrated high resolution (4.5 m footprint) dual-polarization retrievals presented superior accuracy for estimating ground truth moisture under dry conditions with RMSE values between 0.03-0.054 cm³/cm³, and 0.068-0.115 cm³/cm³ after irrigation. Horizontal polarization single retrievals performed favorably against vertical. This study identified improvements for commercial applications and highlighted the potential of sUAS to achieve competent soil moisture and vegetation water content retrievals in semi-arid lands for low canopy land covers.
Subject Area
Remote sensing|Soil sciences|Agricultural engineering
Recommended Citation
Hoyos Echeverri, Santiago, "Microwave Emission Model Parameter Tuning for Surface Soil Moisture Retrieval Using UAV-Mounted Dual Polarization L-Band Radiometer" (2024). ETD Collection for University of Texas, El Paso. AAI31297599.
https://scholarworks.utep.edu/dissertations/AAI31297599