用多角度POLDER数据验证互易原理在遥感像元尺度的适用性

A Test of Reciprocity in Remote Sensing with POLDER Data

利用ADEOS POLDER多角度遥感数据 ,从统计意义出发 ,对光照与观测角度互易的观察对进行考察 ,发现在POLDER数据中存在不可忽略的不互易现象 ,以文中定义的不互易度来衡量 ,可见光波段不互易度可达 1.0 ,红外波段不互易度可达 0 .3。两个方向上计算NDVI的偏差可达 0 .2。分析了不互易度与NDVI和海拔的相关性 ,发现不互易性与地表的复杂程度有一定的相关性 ,并提出地物光谱反射弱的数据不互易度大的假设。

Reciprocity in the sense of “when the Sun and detector change position, the observed reflectance should remain the same”, its validity is tested using ADEOS POLDER level 2 data. Geometrically reciprocal (GR) pairs of data are selected from nearly a months observation of the sample region. It is found that some of these GR pairs have considerable non reciprocity, and ignoring this non reciprocity can cause up to 0.2's uncertainty in the calculation of NDVI. Besides in ratio to wavelength, the magnitute of non reciprocity also shows a sign of correlation with NDVI and altitude. It seems that with IR bands and low NDVI , visible bands and high NDVI , IR bands and high altitude, the data show more non reciprocity.