A Hybrid (Multi-Angle and Multipolarization) Approach to Soil Moisture Retrieval Using the Integral Equation Model: Preparing for the RADARSAT Constellation Mission.

Merzouki, A. and McNairn, H. (2015). "A Hybrid (Multi-Angle and Multipolarization) Approach to Soil Moisture Retrieval Using the Integral Equation Model: Preparing for the RADARSAT Constellation Mission.", Canadian Journal of Remote Sensing, 41(5), pp. 349-362. doi : 10.1080/07038992.2015.1104629  Access to full text

Abstract

The main objective of this research was to develop, test, and validate a soil moisture retrieval method for agricultural fields using C-band synthetic aperture radar (SAR) data in preparation for the RADARSAT Constellation Mission (RCM). The integral equation model (IEM) was used to estimate soil moisture for 12 quad-polarimetric RADARSAT-2 images acquired in 2011 and 2012 over a test site in eastern Canada. A new hybrid inversion scheme is introduced whereby field-level soil moisture retrieval was accomplished through a look-up table (LUT) optimization using backscatter from pairs of RADARSAT-2 data acquired at two incidence angles and two polarizations. The accuracy of this new hybrid approach was compared to that of the more conventional multipolarization inversion. For validation purposes, in situ soil moisture was monitored using a network of four stations designed to capture the maximum soil variability within the study area. Results showed that the hybrid approach provided the best estimates with a mean absolute error of 4.13%. Unlike the multipolarization inversion, the hybrid approach does not require a roughness calibration term. This model/inversion configuration was implemented to produce soil moisture maps from image pairs acquired at different incidence angles. Spatiotemporal changes conveyed by retrieved maps were assessed using an index of absolute normalized moisture difference. The resulting maps provided meaningful information, showing the potential of combining a soil moisture index statistic, IEM, and RADARSAT data in estimating soil moisture conditions. Based on the results presented here, the hybrid approach is well suited for the planned RADARSAT Constellation Mission considering the more frequent relook expected with three satellites. Agriculture and Agri-Food Canada is preparing to implement the hybrid approach to monitor soil moisture across Canada's agricultural landscapes using RCM.

Date modified: