TEMPORAL MONITORING OF SOIL MOISTURE USING ERS-1 SAR DATA

Multi‐temporal synthetic aperture radar (SAR) imagery from the European Remote Sensing Satellite (ERS‐1) was evaluated for monitoring soil moisture at the Romney Marsh test site as part of the UK SAR Calibration and Crop Backscatter Experiment. A total of 18 C‐band (5.3 GHz) ERS‐1 SAR images were acquired during the three day orbit and co‐registered. Accurate calibration of the backscatter measurements was achieved using calibration constants derived from an analysis of corner reflector target responses. Mean backscatter measurements were recorded for each field and compared with field data on soil moisture, surface roughness and rainfall patterns. A comparison of daily and hourly rainfall and soil moisture measurements with backscatter for different cover types showed that the observed trends in backscatter are dominated by moisture effects. A high positive correlation between volumetric soil moisture in the range 10–40% was observed for bare soil fields. A much weaker positive relationship between soil moisture and backscatter was observed for grassland fields.