基于NDVI背景场的雪盖制图算法探索

NDSI算法提取MSS雪盖面积时,受到MSS影像缺少短波红外波段的局限。为充分精确提取MSS影像的雪盖面积,本文探索一种以NDVI为背景场的雪盖制图新思路。该方法首先在辐射校正时利用6S模型反演地表反射率,然后根据各地物的光谱特性差异和NDVI特性差异,在ENVI软件SPECTRAL模块中创建冰雪光谱阈值查找表。通过ETM＋和TM影像的三个例证,详细阐明该算法流程以及查找表的创建,并以NDSI对其雪盖制图进行精度验证。结果一致表明,与常规的分类方法（最大似然法）相比较,本文探索的NDVI背景场算法有更高的总体精度和Kappa系数。

Exploration for the Algorithm of Snow Cover Mapping Based on NDVI Background Field

In the process of obtaining the snow cover area from MSS image with NDSI algorithm,there is a shortcoming that MSS does not have short wave infrared band which can help to distinguish high reflectance of cumulus.To improve the accuracy of obtaining the snow cover area from MSS,this paper explores a method of snow cover mapping based on NDVI background field.Firstly,the land surface reflectance image is derived through 6S model while making radiometric calibration.Then,according to the difference of spectral characteristic and the difference of NDVI characteristic of land objects,we build a Lookup Table on threshold of snow spectrum in the SPECTRAL extension of ENVI software.Through the three demonstrations of ETM+ and TM,the process of algorithm and the way to build LUT are illuminated in detail.And the accuracy of snow cover mapping of this method is tested by NDSI.The results show that the new algorithm has higher Overall accuracy and Kappa Coefficient compared with generally classified method(such as Maximum Likelihood Method).