若尔盖湿地TM影像判识特征

Analysis of TM Imagery Characteristics over Ruoergai Wetland

通过对1994年8月4日与2004年9月16日若尔盖湿地TM影像1-5波段和7波段数据以及归一化植被指数（INDVI）、归一化水指数（INDWI）、归一化水分指数（INDMI）和改进的归一化水指数（IMNDWI）的分析,选择通道7、4、3合成假彩色图作为若尔盖湿地的目视解译图,确定了湿地的TM影像标志。分析结果表明,第7波段能较好地将沙地与其它地物区分,改进的归一化水指数与归一化植被指数之差是非常有效的水体提取因子。还制定了若尔盖湿地主要地物的自动判识流程。判识结果与目视解译结果非常吻合,1994年比1984年湖泊面积、沼泽湿地面积明显减小,而沙化地面积扩大。

The spectrum characteristics of TM band 1 to 5 and band 7, as well as Normalized Difference Vegetation Index, Normalized Difference Water Index, Normalized Difference Moisture Index, and Modified Normalized Difference Water Index, are analyzed by using TM images of 4 August 1994 and 16 September 2004. The false-color images with bands 7, 4 and 3 combined are used to identify the wetland with human eye and the signs of the Ruoergai wetland on the TM imagery are established. The analysis shows that the band 7 can be used to distinguish sandy lands from the other land cover types, and the difference of Modified Normalized Difference Water Index and Normalized Difference Vegetation Index can be used to identify water bodies effectively with the threshold being greater than 0. The better classification result can be obtained automatically. The result shows that compared with in 1984, the area of lake and wetland in 1994 is less obviously, and the area of sandy land is larger.