基于准不变目标物下CBERS-02星CCD图像的交叉定标

Cross Calibration of CBERS-02 CCD Image Based on the Pseudo-invariant Reflectance Targets

提出了一种基于准不变反射率地物的交叉定标方法,首先用MODTRAN模式从已知定标系数的影像中反演出反射率,然后计算出对应未知定标系数影像中相同准不变地物的辐射率,最后求出定标系数。将这种方法应用于CBERS-02卫星CCD影像定标,并用6S模式对CBERS-02和ETM+影像进行大气校正,比较用不同定标系数校正后的地物光谱曲线,得出在高反射率地物下,不同定标系数校正后的地物光谱曲线与ETM+的基本一致;低反射率地物下,单点定标系数误差较大,两点定标系数误差较小,用两点定标系数进行大气校正后植被信息得到明显增强。

This paper illustrates a cross calibration method based on the pseudo-invariant reflectance targets. It can use the images acquired at along interval period, only there is the pseudo-invariant reflectance targets in two images. Firstly, the reflectance was retrieved from the images with known calibration coefficient using MODTRAN model. Secondly, the radiance of the same pseudo-invariant targets in image with unknown calibration coefficient is calculated. Finally, the calibration coefficient is calculated. This method was used on CBERS-02 CCD image calibration. Then the CBERS-02 image using different calibration coefficient and ETM^＋ image were atmospherically corrected using 6S model. The spectral curve of the higher reflectance ground object in CBERS-02 image using different coefficient was accorded to the spectral of the same targets in ETM^＋ image. Under the low reflectance ground object, the single point calibration coefficients error is relatively great rather than the double point calibration coefficient. The vegetation information was enhanced in the image atmospherically corrected using the double points calibration coefficient.