基于HJ-1B数据的积雪制图NDSI阈值分析——以祁连山积雪为例

Analysis on NDSI Threshold in Mapping Snow Cover Based on HJ-1B Data——A Case Study of Snow in the Qilian Mountains

环境减灾卫星是我国于2008年发射的用于环境与灾害监测预报的小卫星星座,相对于气象卫星传感器,其空间分辨率有了较大提高.以祁连山积雪为研究对象,利用环境减灾卫星HJ-1B星开展积雪提取监测研究,分别对不同区域、不同高程的积雪区进行积雪提取,以同时期Landsat ETM+影像中提取的积雪面积为标准,对环境减灾卫星NDSI阈值的选取进行研究分析,以确定适合于HJ-1B提取积雪的阈值;同时利用不同季节的HJ-1B积雪数据进行验证,用Kappa检验阈值的精度.研究表明:HJ-1B积雪制图的阈值为NDSI≥0.24,b2>0.13,b4>0.15;其中,在海拔3 000～4 000m区域NDSI阈值大于0.25,海拔4 001～5 000m区域NDSI阈值大于0.45,海拔5 000m以上区域NDSI阈值大于0.5;利用Kappa检验阈值精度,Khat系数均高于90%,说明该研究确立的HJ-1B数据提取积雪的NDSI阈值合理有效.

The Chinese HJ satellites with smaller constellation,which were launched on September 6,2008,have been improved on spatial resolution.and they are focus on environmental and disaster monitoring and meteorological forecast.In this paper,snow cover of Qilian mountains is exacted at different regions and altitude by means of HJ-1B,meanwhile the optimal threshold of NDSI using HJ satellite is determined through the snow area derived from Landsat ETM ＋ images at same period.At last,the threshold precision are estimated with Kappa test.