Validation of the AIEM Through Correlation Length Parameterization at Field Scale Using Radar Imagery in a Semi-Arid Environment

Abstract

Abstract-This work aimed to validate the Advanced Integral Equation Model (AIEM) through different correlation length parameterizations using radar imagery for field-scale studies in a semi-arid environment. The study compared backscattering coefficients simulated from the AIEM and retrieved from SAR imagery of a study site in Sardinia. Two treatments for correlation length were adopted: in situ measurements and empirically based correlation length estimation. The results showed an overestimation of backscattering coefficients of 2.5 dB with an RMSE of 3.1 dB for HH and VV polarizations and an underestimation of 27.7 dB and an RMSE of 31.0 dB for HV polarization from the AIEM parameterized by in situ measurements. When using the AIEM with empirical correlation length, a bias of less than 1.0 dB was found with an RMSE of 1.7 dB for HH and VV polarizations and an overestimation of 1.1 dB and an RMSE of 5.1 dB for HV polarization. Better results were obtained with surface soil moisture (SSM) measured at 10 cm than at 5 cm. Promising soil moisture data retrieval from SAR imagery is expected from using the empirical correlation length-parameterized AIEM for field-scale purposes in semi-arid environments.

Remote sensing for mapping soil moisture and drainage potential in semi-arid regions: Applications to the Campidano plain of Sardinia, Italy

“…Some researchers work at field scale using theoretical inversion models with radar images Brogioni et al, 2010;Dong et al, 2013;Nearing et al, 2010;Wu et al, 2008). Those studies are essential to the understanding of radar signal interaction with soil parameters in order to improve the estimation of surface SM for various ground types.…”

Evaluation of the Oh, Dubois and IEM Backscatter Models Using a Large Dataset of SAR Data and Experimental Soil Measurements

“…Several studies confirmed that the use of the calibrated correlation length, as proposed by Baghdadi et al [14][15][16][17][18][19] is able to improves the performance of the IEM at both both HH and VV polarizations [35][36][37]. Dong et al [36] used the calibrated correlation length in the AIEM to simulate SAR data in C-band.…”

“…Several studies showed that the use of the fitting parameter Lopt allows more correct estimations of the radar backscattering coefficient [36].…”

“…Dong et al [36] used the calibrated correlation length in the AIEM to simulate SAR data in C-band. Results showing that the RMSE reduced from 3.1 to 1.7 dB at HH and VV polarizations and from 31.0 to 5.1 dB at HV polarization.…”

A Global Sensitivity Analysis of Soil Parameters Associated With Backscattering Using the Advanced Integral Equation Model

“…The model is capable of simulating the scattering by and emissions from the natural land surface for a wide range of dielectric and roughness conditions and remote sensor configurations. The model is highly accurate and has been widely used in microwave scattering and emission analyses and soil moisture retrieval [8], [17], [18]. Compared with the IEM, two improvements have been incorporated into the AIEM: 1) it includes complete expressions for the Kirchhoff field coefficient and complementary field coefficient (see Fig.…”