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首页> 外文期刊>Zeitschrift fur Gletscherkunde und Glazialgeologie >Semi-automatic glacier delineation from Landsat imagery over Hintereisferner in the Austrian Alps
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Semi-automatic glacier delineation from Landsat imagery over Hintereisferner in the Austrian Alps

机译：在奥地利阿尔卑斯山的Hintereisferner上从Landsat影像进行的半自动冰川定界

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摘要

In this study a procedure is presented to semi-automatically derive glacier delineations from Landsat satellite imagery for Hintereisferner, a glacier in the Austrian Alps. Spectral information inherent to imagery was utilised to derive the masks and existing manual glacier outlines from maps served as reference data for validation of masks for the years 1991 and 1997 Within the first step of the model a water mask is created. It requires as input the raw satellite image and an upper range of 20-30% of Digital Number value counts in the histogram of the Normalised Difference Water Index. The second step, which creates the glacier mask, requires as input the raw satellite image and the water mask. It uses a threshold value for (E)TM(±)5 to mask clouds and assumes saturated pixels to be glacier if not identified as clouds Finally it automatically calculates a Normalised Difference Snow Index threshold value of 0.5-0.7 based on the variable range in Digital Number values for each image After performing accuracy analyses omissions ±17% and ±13% for the years 1991 and 1997 were found. The omissions were located at the margins of the glacier where debris on the surface prohibited a spectral differentiation between glacier and nearby slopes. A change analysis for the period 1991-1997 revealed an omission of 16 % in unchanged area for the surface of Hintereisferner. The area of Hintereisferner was determined within a range of-10.8% and ±8.7% when compared to conventional photogram-metric measurements. In the period 1985-1999 the area of Hintereisferner and its neighbouring glaciers decreased from 159 km2 to 138 km2. During the reference period 1991-1997 the decrease was 6 km2.
机译：在这项研究中，提出了一种程序，可从Landsat卫星图像中半自动得出奥地利阿尔卑斯山冰川Hintereisferner的冰川轮廓。利用图像固有的光谱信息从地图中得出了口罩和现有的手动冰川轮廓，作为1991年和1997年口罩验证的参考数据。在模型的第一步中，创建了一个水口罩。它要求输入原始卫星图像和归一化差异水指数直方图中数字值计数上限的20-30％。创建冰川蒙版的第二步需要输入原始卫星图像和水蒙版作为输入。它使用（E）TM（±）5的阈值来遮盖云层，并且如果未将其识别为云层，则认为饱和像素将变得更加冰川。最后，它会根据其中的可变范围自动计算标准化差雪指数阈值0.5-0.7每个图像的数字值经过精确度分析后，发现1991年和1997年的遗漏值分别为±17％和±13％。遗漏位于冰川的边缘，那里的表面碎屑阻止了冰川与附近斜坡之间的光谱差异。 1991年至1997年期间的变化分析显示，辛特芬公司表面未改变的区域遗漏了16％。与传统的摄影测量相比，辛特芬的面积被确定在10.8％和±8.7％的范围内。在1985-1999年期间，辛特奈斯费尔纳及其附近的冰川面积从159 km2减少到138 km2。在1991-1997年的参考期间，减少了6 km2。

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