Evaluation of the Dubois, Oh, and IEM radar backscatter models over agricultural fields using C-band RADARSAT-2 SAR image data

Backscatter from synthetic aperture radar (SAR) is correlated with surface characteristics such as soil dielectric properties, surface roughness, and vegetation cover. The purpose of this study is to evaluate the capability of surface radar backscatter models to estimate soil moisture over agricultural fields from fully polarimetric RADARSAT-2 C-band SAR responses. For validation purposes, ground measurements over 44 and 42 sampling sites in eastern Ontario and southern Manitoba, respectively, were carried out in the spring of 2008 simultaneous with satellite data acquisitions. A comparison was made between the backscatter coefficient results derived from three scattering models (the semi-empirical models of Dubois and Oh and the theoretical integral equation model (IEM)) and the SAR image backscatter. Discrepancies between measured radar backscatter coefficients and those predicted by the models have been investigated. Overall, the results show that semi-empirical approaches tend to overestimate the radar response, but correction factors of about 3.5 and 2.0 dB, respectively, were found sufficient to correct the Dubois HH and VV backscatter coefficients. The Oh model backscatter estimations were less variable than those derived from the Dubois model; however, a correction factor of about 5.0 dB was necessary in this case. Data simulated by the IEM showed significant fluctuations. This result was somewhat expected, since previous studies have shown that correlation length measurements are very sensitive to profile length, and a relatively short profile length was used in this study. Correlation agreements were significantly improved when using the IEM semi-empirical calibration technique. These results indicate that further work is needed to assess the requirement for correction factors, such that these models can be operationally implemented to estimate soil moisture in support of agricultural monitoring.

[1]  M. S. Moran,et al.  Comparison of four models to determine surface soil moisture from C‐band radar imagery in a sparsely vegetated semiarid landscape , 2006 .

[2]  B. Surv,et al.  ESTIMATING SOIL MOISTURE PROFILE DYNAMICS FROM NEAR-SURFACE SOIL MOISTURE MEASUREMENTS AND STANDARD METEOROLOGICAL DATA , 2000 .

[3]  Malcolm Davidson,et al.  Parameterization of tillage-induced single-scale soil roughness from 4-m profiles , 2006, IEEE Transactions on Geoscience and Remote Sensing.

[4]  A. Bannari,et al.  Caractérisation géostatistique de la variabilité spatiale de l’humidité du sol à l’aide des cartes dérivées des données radar à synthèse d’ouverture de RADARSAT-1 , 2008 .

[5]  Pascale C. Dubois,et al.  Measuring soil moisture with imaging radars , 1995, IEEE Trans. Geosci. Remote. Sens..

[6]  F. Ulaby,et al.  Handbook of radar scattering statistics for terrain , 1989 .

[7]  Malcolm Davidson,et al.  On the characterization of agricultural soil roughness for radar remote sensing studies , 2000, IEEE Trans. Geosci. Remote. Sens..

[8]  E. Engman,et al.  Status of microwave soil moisture measurements with remote sensing , 1995 .

[9]  Richard K. Moore,et al.  Active microwave measurement of soil water content , 1974 .

[10]  Critical Infrastructure Protection and Emergency Preparedness , 2022 .

[11]  M. S. Moran,et al.  Appropriate scale of soil moisture retrieval from high resolution radar imagery for bare and minimally vegetated soils , 2008 .

[12]  Jeffrey P. Walker,et al.  Profile soil moisture estimation using the modified IEM , 1997, IGARSS'97. 1997 IEEE International Geoscience and Remote Sensing Symposium Proceedings. Remote Sensing - A Scientific Vision for Sustainable Development.

[13]  Jin-Young Hong,et al.  Effect of Surface Profile Length on the Backscattering Coefficients of Bare Surfaces , 2007, IEEE Transactions on Geoscience and Remote Sensing.

[14]  Niko E. C. Verhoest,et al.  Influence of Surface Roughness Spatial Variability and Temporal Dynamics on the Retrieval of Soil Moisture from SAR Observations , 2009, Sensors.

[15]  Claude R. Duguay,et al.  Reviewing the Role of Radar in Mapping Soil Management Practices , 1998 .

[16]  T. Jackson,et al.  Remote sensing applications to hydrology: soil moisture , 1996 .

[17]  Mehrez Zribi,et al.  Soil moisture mapping based on ASAR/ENVISAT radar data over a Sahelian region , 2007 .

[18]  T. Manninen,et al.  Measuring the roughness characteristics of natural surfaces at pixel scales: moving from 1 metre to 25 metre profiles , 1998, IGARSS '98. Sensing and Managing the Environment. 1998 IEEE International Geoscience and Remote Sensing. Symposium Proceedings. (Cat. No.98CH36174).

[19]  P. Paillou,et al.  Relationship between profile length and roughness variables for natural surfaces , 2000 .

[20]  Y. Kerr,et al.  Use of passive microwave remote sensing to monitor soil moisture , 1998 .

[21]  Yisok Oh,et al.  Condition for precise measurement of soil surface roughness , 1998, IEEE Trans. Geosci. Remote. Sens..

[22]  Yann Kerr,et al.  Estimating surface soil moisture and soil roughness over semiarid areas from the use of the copolarization ratio , 2001 .

[23]  Mehrez Zribi,et al.  Calibration of the Integral Equation Model for SAR data in C‐band and HH and VV polarizations , 2006 .

[24]  N. O'Neill,et al.  Thermal infrared remote sensing of soils: Evolution, trends and perspectives , 1993 .

[25]  Francesco Mattia,et al.  Hydrology and Earth System Sciences Soil Moisture Retrieval through a Merging of Multi-temporal L-band Sar Data and Hydrologic Modelling , 2022 .

[26]  Jesús Álvarez-Mozos,et al.  Evaluation of empirical and semi-empirical backscattering models for surface soil moisture estimation , 2007 .

[27]  Kamal Sarabandi,et al.  An empirical model and an inversion technique for radar scattering from bare soil surfaces , 1992, IEEE Trans. Geosci. Remote. Sens..

[28]  Yisok Oh,et al.  Quantitative retrieval of soil moisture content and surface roughness from multipolarized radar observations of bare soil surfaces , 2004, IEEE Transactions on Geoscience and Remote Sensing.

[29]  Fawwaz T. Ulaby,et al.  Dielectric properties of soils in the 0.3-1.3-GHz range , 1995, IEEE Trans. Geosci. Remote. Sens..

[30]  Wolfgang Wagner,et al.  On the Soil Roughness Parameterization Problem in Soil Moisture Retrieval of Bare Surfaces from Synthetic Aperture Radar , 2008, Sensors.

[31]  M. S. Dawson,et al.  A modified IEM model for: scattering from soil surfaces with application to soil moisture sensing , 1996, IGARSS '96. 1996 International Geoscience and Remote Sensing Symposium.

[32]  Thuy Le Toan,et al.  Joint statistical properties of RMS height and correlation length derived from multisite 1-m roughness measurements , 2003, IEEE Trans. Geosci. Remote. Sens..

[33]  Jiancheng Shi,et al.  Estimation of bare surface soil moisture and surface roughness parameter using L-band SAR image data , 1997, IEEE Trans. Geosci. Remote. Sens..

[34]  A. Fung.  Microwave Scattering and Emission Models and their Applications , 1994 .

[35]  Thomas J. Jackson,et al.  Mapping surface roughness and soil moisture using multi-angle radar imagery without ancillary data , 2008 .

[36]  Thuy Le Toan,et al.  A comparison between soil roughness statistics used in surface scattering models derived from mechanical and laser profilers , 2003, IEEE Trans. Geosci. Remote. Sens..

[37]  Jiancheng Shi,et al.  A Comparison of Soil Moisture Retrieval Models Using SIR-C Measurements over the Little Washita River Watershed , 1997 .

[38]  Adrian K. Fung,et al.  Backscattering from a randomly rough dielectric surface , 1992, IEEE Trans. Geosci. Remote. Sens..

[39]  Urs Wegmüller,et al.  Active and passive microwave signature catalog on bare soil (2-12 GHz) , 1994, IEEE Trans. Geosci. Remote. Sens..

[40]  Mehrez Zribi,et al.  Evaluation of radar backscatter models IEM, OH and Dubois using experimental observations , 2006 .

[41]  C. Willmott.  Some Comments on the Evaluation of Model Performance , 1982 .

[42]  Thuy Le Toan,et al.  The effect of surface roughness on multifrequency polarimetric SAR data , 1997, IEEE Trans. Geosci. Remote. Sens..

[43]  Roger D. De Roo,et al.  A semi-empirical backscattering model at L-band and C-band for a soybean canopy with soil moisture inversion , 2001, IEEE Trans. Geosci. Remote. Sens..

[44]  Ross Bryant,et al.  Measuring Surface Roughness Height to Parameterize Radar Backscatter Models for Retrieval of Surface Soil Moisture , 2007, IEEE Geoscience and Remote Sensing Letters.

[45]  M. Sahebi,et al.  A comparison of multi-polarization and multi-angular approaches for estimating bare soil surface roughness from spaceborne radar data , 2002 .

[46]  Dawei Han,et al.  Automated Thiessen polygon generation , 2006 .

[47]  E. Njoku,et al.  Passive microwave remote sensing of soil moisture , 1996 .

[48]  C. Ottlé,et al.  Surface soil moisture estimation from the synergistic use of the (multi-incidence and multi-resolution) active microwave ERS Wind Scatterometer and SAR data , 2003 .

[49]  Robert H. Woodward,et al.  Determining Soil Moisture from Geosynchronous Satellite Infrared Data: A Feasibility Study , 1984 .

[50]  M. Sahebi,et al.  Semi-empirical calibration of the IEM backscattering model using radar images and moisture and roughness field measurements , 2004 .