Radiometric Cross-calibration of CBERS-02 WFI with MODIS and the Effect on VI
CBERS-02 WFI的辐射交叉定标及其对植被指数的作用

With the MODIS as a reference sensor,the radiometric cross-calibration was performed for(CBERS-02) WFI and the calibration coefficients and the offsets were obtained.The offsets for both channels were very large,about 42 and 21 respectively.For validation,the calibration results were applied to another region of WFI image to get the apparent reflectance,which was compared to the one from MODIS image.The differences for both two corresponding channels were 3.6% and-3.6%,which demonstrated that the calibration results we got should satisfy the quantitative application.Five experimental regions from WFI images were selected to calculate their vegetation index both before and after radiometric calibration and the comparison showed that the degree of fitting using the quadratic polynomial function could reach 99% after the offsets were subtracted from the original DNs.The comparison between the NDVI and RVI from WFI and those derived from MODIS illustrated clearly that the VI derived from the WFI with calibration coefficients were much closer to those of MODIS and the variation of the RVI between two sensors was smaller than that of the NDVI.