中文摘要：

基于水流路径分析的思路，提出一种雪线自动提取方法。该方法利用对水流路径上积雪覆盖信息逐像元对比，记录最下点位置形成积雪区下边缘点，顺次连接各点形成雪线；在此基础上，探讨了多年平均雪线的求算。研究表明，该方法可避免雪盖内部积雪空缺区域对下边缘线提取的影响，较好地提取积雪区的下边缘线，初步实现了雪线的数字提取；并可较为方便地进行多个时期雪线的时空变化对比分析。利用该方法并结合遥感影像数据，可为大范围雪线时空分异信息的快速、准确提取与分析奠定基础。

英文摘要：

In this paper, a digital identification method for a snowline is presented. The method takes into consideration that the lower limits of a perennially snow-covered area should only be deduced through .contrasting with other limits. Thus, a method based on hydrological analysis was introduced to extract the snowline. Based on the digital elevation model （DEM） of the study area and the result of snow cover monitoring, the lowest point covered with snow could be recorded in one flow path. Through loop statements, all of the lowest points were determined by comparing the snow altitude in every flow path. The lowest points were then joined sequentially, according to the real landform, and shaped into snowlines. In addition, a method of computing the average annual snowline was analyzed. This method based on hydrological analysis can effectively avoid the influence of naked areas in snow cover, and shows promising results for the calculation of the lower boundary of a perennially snow-covered area. Spatial-temporal dynamics of snowlines can also be analyzed by the proposed method. The digital identification method presented here is effective at identifying a snowline, and could be helpful in rapid information extraction of a large-scale area.