期刊名称：ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
印刷版ISSN：2194-9042
电子版ISSN：2194-9050
出版年度：2007
卷号：XXXVI-7/C50
出版社：Copernicus Publications
摘要：An often neglected source of uncertainty on estimated cover percentage is caused by local view angle effects, where parts of bare soil patches are not visible due to vegetation blocking the sensor line-of-sight. When estimating the fractional cover of pixels far off- nadir or at slopes pointing away from the sensor, plant cover can be overestimated by more than 50%, seriously decreasing the accuracy. This problem is inherent when using wide field of view (FOV) sensors, or satellite sensors tilted off-nadir. In the following, results of a study using airborne HyMap hyperspectral data with a wide FOV of ±32° are presented. Ground cover fractions for bare soil, green (PV) and dry (NPV) vegetation were derived using an iterative multiple endmember spectral mixture analysis (MESMA) approach. Using field measurements of geometric canopy parameters as well as terrain information, typical error margins of local incidence angle effects on unmixing results were calculated. These results are further included as a component in a per-pixel accuracy estimate to be introduced
