雪盖指数法提取积雪范围信息的不确定性研究——以玛纳斯上游地区为例

Accuracy and Uncertainty of Snow Information based on NDSI ——A Case Study of Upstream Region of Manas River

基于2006年9月10日空间分辨率为30m的TM影像与DEM数据,通过雪盖指数法自动提取积雪范围与目视解译结果进行对比,以粗糙度为度量,定性、定量分析影响其不确定性的地表覆被和地形因素。结果表明:①当NDSI阈值取0.57~0.72和0.4~0.8时,结果有明显差异,取0.57~0.72时漏分像元比0.4~0.8稍多,但是误分像元大幅减少;②同处于阴影区裸地的光谱曲线与积雪的光谱曲线相似,造成阴影区的积雪与裸地不能正确区分,此外处于阴影区域的植被由于反射率较低,使其NDSI刚好在阈值范围内,被误分为积雪;③半阴坡雪盖指数法提取积雪的不确定性最小,而阳坡、半阳坡雪盖指数法提取积雪的不确定性最大;④雪盖指数法提取积雪的不确定性随着坡度的增加呈下降趋势,即坡度越大不确定性越小。

With the deepening of the research and application of remote sensing,the quality of remote sensing data as well as the uncertainty problem has caused wide attention,especially the combination between remote sensing information and GIS makes the research content and system of the uncertainty of remote sensing,the source of data uncertainty,processing method etc,which has become a hotspot in the field of remote sensing.Based on the spatial resolution of 30mof TM images and DEM data on September 10, 2006,this study automatic extract the scope of the snow by the method of NDSI,then compare with the result of visual interpretation,taking roughness as measurement,analyse land cover and terrain factor which affect its uncertainty.The results show that:The bare land's spectrum curve and the snow spectrum curve are in the shadow area are very similar,so it's hard to distinguish bare land from snow in this area,in addition,the vegetation in shadow area are misclassification as snow because of their low reflectivity;Extract the scope of the snow by the method of NDSI in half shady slope,its uncertainty is the minimum,but in sunny slope and half sunny slope the uncertainty is the maximum.The uncertainty of extract the scope of the snow by the method of NDSI is smaller when the slope is bigger.