Evaluation of RISAT-1 data for soil moisture retrieval in semi-arid tropics of India

Abstract

The selection of better polarisation and incidence angle for soil moisture retrieval using RISAT-1 microwave data was experimented at Hayathnagar research farm of ICAR-CRIDA, Hyderabad. Fine Resolution Sensor (FRS-1) data (spatial resolution of 3 m) and Medium Resolution ScanSAR (MRS) data (spatial resolution of 25 m) acquired from circular and dual polarised microwave data were used for the retrieval of soil moisture and to identify the best polarisation suitable for the study area. The evaluation was carried out during 2016-17. FRS-1 data was more accurate than MRS data for the extraction of soil moisture in the study area. Circular and dual-Polarisation retrieved soil moisture values were compared with volumetric soil moisture values for assessing the better polarisation. Dual polarisation and the incident angle between 15-20 degrees with R2=0.952 performed better as compared to circular polarisation with more or less than 20 degrees' incident angle. A correction factor of -0.723 was derived and applied to FRS-1 data with less than a 20-degree incident angle for getting real soil moisture values on the spatio-temporal basis to optimize the management of natural ecosystems under climate change threat.

Keywords

• Microwave remote sensing
• RISAT-1
• Soil moisture