An inversion method based on multi-angular approaches for estimating bare soil surface parameters from RADARSAT-1

Abstract

Abstract. The radar signal recorded by earth observation (EO) satellites is sensitive to soil moisture and surface roughness, which both influence the onset of runoff.This paper focuses on inversion of these parameters using a multi-angular approach based on RADARSAT-1 data with incidence angles of 35 • and 47 • (in mode S3 and S7). This inversion was performed with three backscatter models: Geometrical Optics Model (GOM), Oh Model (OM), and Modified Dubois Model (MDM), which were compared to obtain the best configuration. Mean absolute errors of 1.23, 1.12, and 2.08 cm for roughness expressed in rms height and for dielectric constant, mean absolute errors of 2.46 -equal to 3.88 (m 3 m −3 ) in volumetric soil moisture, -4.95 -equal to 8.72 (m 3 m −3 ) in volumetric soil moisture -and 3.31 -equal to 6.03 (m 3 m −3 ) in volumetric soil moisture -were obtained for the MDM, GOM, and OM simulation, respectively. These results indicate that the MDM provided the most accurate data with minimum errors. Therefore, the latter inversion algorithm was applied to images, and the final results are presented in two different maps showing pixel and homogeneous zones for surface roughness and soil moisture.

Assessment of Different Backscattering Models for Bare Soil Surface Parameters Estimation from SAR Data in band C, L and P

“…It should be noted that for each model there are some restrictions to use. For each model there are some validity range which are presented in different researches such as Dubois et al [1995], Ulaby et al [1981], Sahebi et al [2002], and Sahebi et al [2010].…”

“…To evaluate dielectric constant and roughness using the Dubois model, the inverse model was used [Sahebi and Angles, 2010]. These two parameters were also calculated using the Oh model and iteration [Oh et al, 1992].…”

“…Findings by Alvarez-Mozos et al [2007] showed that using multi-polarized data, dielectric constant and surface roughness could be estimated without in-situ measurements. Sahebi and Angles [2010] compared the Geometrical Optics Model (GOM), Physical Optic Model (POM), Oh Model, and Modified Dubois Model (MDM) using multi-angular RADARSAT and reported that MDM is the most versatile model for retrieving soil surface parameters. They also indicated that multi-angular data are more effective than multi-polarization data and that IEM is the most accurate model compared with the others [Sahebi et al, 2004].…”

Advances in soil moisture retrieval from synthetic aperture radar and hydrological applications

“…For high incidence angles and rough surfaces, the Oh model accurately estimated backscatter for the co-polarization ratio ) and for all polarizations at C band using RADARSAT data (Álvarez-Mozos et al, 2007). In contrast, some studies have found that the Oh model tends to overestimate radar backscatter for the crosspolarization or all polarizations (Merzouki et al, 2010;van Oevelen and Hoekman, 1999), whereas many others have found it tends to underestimate observed backscatter (Boisvert et al, 1997;Gherboudj et al, 2009Gherboudj et al, , 2011Merzouki et al, 2011;Sahebi and Angles, 2010). It was noted by several authors that the bias in the Oh model for a specific study area could be accounted for by applying a correction factor De Roo et al, 2001;D'Urso and Minacapilli, 2006;Merzouki et al, 2010), although more work is required to develop correction factors to operationally implement the Oh model for soil moisture retrieval (Merzouki et al, 2010).…”

The Potential Use of Multi-Band SAR Data for Soil Moisture Retrieval over Bare Agricultural Areas: Hebei, China

“…The original Dubois model needs HH and VV polarization SAR data as inputs to estimate soil moisture content. Sahebi and Angles [26] developed the Dubois model to estimate soil moisture content based on single polarization SAR data with two incidence angles. In this study, the modified Dubois model based on multi-band SAR data was developed and used to estimate soil moisture content independent of surface roughness.…”