ASTER GDEM V2的南极冰川高程误差校正及精度分析

Vertical accuracy correction and analysis of ASTER GDEM V2 over Antarctic Glacier

ASTER GDEM V2是研究南极冰盖表面的一种重要DEM数据源。由于南极冰雪区反射率高且缺乏地形特征,导致ASTER GDEM V2存在大量的坑、隆起等噪声,难以直接用于南极地形分析。本文以ICESat/GLAS激光点高程数据作为参考,采用修正等高线法对南极伯德(Byrd)冰川ASTER GDEM V2进行了误差校正,并将其与ICESat-1 DEM的垂直精度进行了对比分析。结果表明:ASTER GDEM V2的RMSE由校正前的26.56 m下降到校正后的18.77 m,远低于ICESat-1 DEM的RMSE(121.24 m);校正后的ASTER GDEM V2高程精度受坡度影响较小,不存在明显的系统误差,而ICESat-1 DEM的高程精度受坡度的影响较大。本研究进一步通过地形剖面分析得到:校正前的ASTER GDEM V2噪声主要分布于高程较低、地形平坦的区域,通过修正等高线的方法可以有效去除这些噪声,去除噪声后的ASTER GDEM V2可作为研究伯德冰川理想的DEM数据源。

ASTER GDEM V2 is one of the most widely used DEM data for Antarctic Ice Sheet analysis.However,it cannot be directly used due to its large anomalies in the snow-covered plateaus of the continent,where the surface reflectance is very high and no obvious surface features are available for the generation of high-quality DEM.This study rectifies the large anomalies in ASTER GDEM V2 over Byrd Glacier using a contour correction method.Then the accuracy of the anomaly-corrected ASTER GDEM V2 is quantitatively evaluated against.Results show that the RMSE of ASTER GDEM V2 decreases from 26.56 m to 18.77 m(-6.79 m),which is lower than the RMSE of ICESat-1 DEM(121.24 m).In addition,the accuracy of the corrected ASTER GDEM V2 is barely influenced by slope and no significant systematic errors can be observed.In contrast,the accuracy of ICESat-1 DEM is very sensitive to slope.Through further topographic profile analysis,the noises on previously non-corrected ASTER GDEM V2 are found to be mainly distributed in the low flat areas.Those noises can be effectively removed by using the contour correction method.This study indicates that the corrected ASTER GDEM V2 is well qualified for analyzing Byrd Glacier,Antarctica.