transmissivity is computed using NDWI from Landsat TM, 
then, volume and interaction scatter are removed from 
observations based on some assumptions, finally, soil moisture 
4 
change estimation algorithm is developed using surface scatter 
at two acquisitions. The results are validated using in-situ 
samples of 0-1 cm. The results showed than the algorithm can 
1 Measured 
4 
R=0.85 
• 
• 
• 
•• .!/ 
Com 
L-W 
easurecl 
Fig.2 The Validation of results for both soybean and com field at four polarizations 
be used at L-band, but not at S-band. It is the key in future 
work that the algorithm will be advanced to be used at higher 
frequency. 
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ACKNOWLEDGEMENTS: 
This work was supported by funds from NSFC and CAS under 
grants 40671140 and kzcx2-yw-301. The EnviSat ASAR data 
were provided by ESA through the Category-1 ID: 1406.