Comparison of HJ-1A CCD and TM data and for estimating grass LAI and fresh biomass
HJ-1A CCD与TM数据及其估算草地LAI和鲜生物量效果比较分析

Based on field measurements and the PROSAIL model simulations, this paper compared the new HJ-1A CCDs sensors data and the widely used TM data, and analyzed the effects of the sensors zenith angle and spectral response function (SRF). We further compared the two sensors in estimating grass LAI and fresh biomass. The following conclusions can be drawn: (1) the adjusted coefficients of determination R2 between HJ-1A CCDs and TM reflectance ranged from 0.7322 to 0.9205. The reflectance of the two sensors are very consistent while the absolute value is small, but as the grass cover faction increases, HJ-1A CCDs data is a little larger than TM. Overall, for the visible and near infrared bands, the HJ-1A CCDs image data is generally similar to the TM data. For HJ-1A CCDs and TM, the reflectance in red band showed the best correlation. (2) The normalized difference vegetation index (NDVI) of HJ-1A CCDs and TM are signif icantly correlated. Compared with reflectance data (with relative difference of 3.34%-9.54%), NDVI is less affected (with relative difference of 0.34%-0.53%) by sensor zenith angle or spectral response function. (3) The sensor zenith angle was proved making a slightly greater impact on the sensor reflectance data than the spectral response function. (4) HJ-1A CCDs reflectance data exhibited good correlations with grass LAI and fresh biomass, and HJ-1A CCD2 data performed the best.