Digital elevation model (DEM) of the ice sheet in western Dronning Maud Land, Antarctica

In this paper, a new digital elevation model (DEM) is derived for the ice sheet in western Dronning Maud Land, Antarctica. It is based on differential interferometric synthetic aperture radar (SAR) from the European Remote Sensing 1/2 (ERS-1/2) satellites, in combination with ICESat's Geoscience Laser Altimeter System (GLAS). A DEM mosaic is compiled out of 116 scenes from the ERS-1 ice phase in 1994 and the ERS-1/2 tandem mission between 1996 and 1997 with the GLAS data acquired in 2003 that served as ground control. Using three different SAR processors, uncertainties in phase stability and baseline model, resulting in height errors of up to 20 m, are exemplified. Atmospheric influences at the same order of magnitude are demonstrated, and corresponding scenes are excluded. For validation of the DEM mosaic, covering an area of about 130,000 km**2 on a 50-m grid, independent ICESat heights (2004-2007), ground-based kinematic GPS (2005), and airborne laser scanner data (ALS, 2007) are used. Excluding small areas with low phase coherence, the DEM differs in mean and standard deviation by 0.5 +/- 10.1, 1.1 +/- 6.4, and 3.1 +/- 4.0 m from ICESat, GPS, and ALS, respectively. The excluded data points may deviate by more than 50 m. In order to suppress the spatially variable noise below a 5-m threshold, 18% of the DEM area is selectively averaged to a final product at varying horizontal spatial resolution. Apart from mountainous areas, the new DEM outperforms other currently available DEMs and may serve as a benchmark for future elevation models such as from the TanDEM-X mission to spatially monitor ice sheet elevation.

本研究针对南极洲德龙宁毛德地区西部的冰盖构建了一套全新的数字高程模型（Digital Elevation Model, DEM）。该模型基于欧洲遥感1/2号（European Remote Sensing 1/2, ERS-1/2）卫星的差分干涉合成孔径雷达（differential interferometric synthetic aperture radar, SAR）数据，并结合了ICESat的地球科学激光测高系统（Geoscience Laser Altimeter System, GLAS）数据。研究整合了1994年ERS-1冰相模式下的116景影像、1996至1997年ERS-1/2联飞任务的影像，以及2003年获取的GLAS地面控制点数据，最终合成DEM镶嵌图。本研究采用三款不同的SAR处理器开展处理，验证了相位稳定性与基线模型存在的不确定性，其引发的高程误差最高可达20米；同时证明大气影响的量级与之相当，因此对应的影像景已被剔除。该DEM镶嵌图覆盖面积约13万平方千米，格网分辨率为50米。为验证其精度，研究采用了独立获取的ICESat高程数据（2004-2007年）、地面动态GPS（2005年）以及机载激光扫描数据（airborne laser scanner, ALS，2007年）。剔除相位相干性较低的小片区域后，该DEM与ICESat、GPS及ALS数据的平均偏差及标准差分别为0.5±10.1米、1.1±6.4米及3.1±4.0米。被剔除的数据点偏差可能超过50米。为将空间可变噪声抑制至5米阈值以下，研究对18%的DEM区域进行选择性平均，最终生成具备不同水平空间分辨率的成品。除山区外，这套全新的DEM精度优于当前其他可用的DEM产品，可作为未来高程模型（如TanDEM-X任务获取的模型）的基准，用于空间监测冰盖高程变化。