Surface heights and crevasse morphologies of surging and fast-moving glaciers from ICESat-2 laser altimeter data - Application of the density-dimension algorithm (DDA-ice) and evaluation using airborne altimeter and Planet SkySat data
Surface heights and crevasse morphologies of surging and fast-moving glaciers from ICESat-2 laser altimeter data - Application of the density-dimension algorithm (DDA-ice) and evaluation using airborne altimeter and Planet SkySat data
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DOI：
10.1016/j.srs.2020.100013
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发表时间：
2021-06
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影响因子：
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通讯作者：
U. Herzfeld;T. Trantow;Matthew Lawson;J. Hans;G. Medley
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文献类型：
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作者：
U. Herzfeld;T. Trantow;Matthew Lawson;J. Hans;G. Medley
2018年9月15日发射的美国宇航局冰、云和陆地高程卫星ICESat-2携带了第一个星载多光束微脉冲光子计数激光高度计系统，即先进地形激光高度计系统（ATLAS）。ATLAS的观测是在三对弱和强光束中获得的，标称沿轨道间距为0.7米（在晴朗的天空条件下）。将观测记录为光子点云，其中包括信号和背景/噪声事件，需要一种专用算法来识别信号光子和确定表面高度。本文的目的是证明，ICESat-2的测量可以确定高度严重裂缝的冰面和产量的海拔剖面，目前的形态特征是典型的快速移动和加速冰川。从光子点云的表面高度的确定是由冰表面的密度维算法，DDA冰。DDA-ice以0.7米的传感器分辨率返回强光束和弱光束的表面高度，它利用径向基函数进行数据汇总，并自动适应不断变化的环境条件和背景特征，包括一天中的时间和表观表面反射率。相比之下，官方的陆地冰沿轨高度产品ATL 06提供了40米分辨率的表面高度，20米的帖子。DDA-ice信号分类一致地识别了来自强和弱ATLAS光束中复杂反射体的光子，因此比ATL 03全球地理定位光子产品的信号分类有了显著的进步。结果进行评估使用（1）机载激光高度计数据收集在我们的ICESat-2验证活动在Negribreen，斯瓦尔巴群岛，在浪涌期间，和（2）高分辨率（0.72米或0.86米）的卫星图像数据从行星SkySat获得的伊卢利萨特冰流（雅各布港Isbravn），格陵兰岛。ICESat-2数据利用DDA冰分析，可以根据形态特征区分冰表面类型与涌动的冰川（Negribreen）和持续快速移动和加速的冰川（Jakobshavn Isbrün）。
NASA’s Ice, Cloud and land Elevation Satellite ICESat-2, launched September 15, 2018, carries the first space-borne multi-beam micro-pulse photon-counting laser altimeter system, the Advanced Topographic Laser Altimeter System (ATLAS). Observations from ATLAS are acquired in three pairs of weak and strong beams with 0.7 m nominal along-track spacing (under clear-sky conditions). The recording of the observations as a photon point cloud, which includes signal and background/noise events, requires a dedicated algorithm for identification of signal photons and determination of surface heights. The objectives of this paper are to demonstrate that measurements from ICESat-2 allow determination of heights over heavily crevassed ice surfaces and yield elevation profiles that present morphological characteristics that are typical of fast-moving and accelerating glaciers. Surface-height determination from the photon point cloud is facilitated by the density-dimension algorithm for ice surfaces, the DDA-ice. The DDA-ice returns surface heights at the 0.7 m sensor resolution for strong and weak beams, it utilizes a radial basis function for data aggregation and automatically adapts to changing environmental conditions and background characteristics, including time of day and apparent surface reflectance. In contrast, the official Land-Ice Along-Track Height Product, ATL06, provides surface heights at 40 m resolution with 20 m postings. The DDA-ice signal classification consistently identifies photons from complex reflectors in both the strong and weak ATLAS beams and hence constitutes a significant advance over the signal classification on the ATL03 Global Geolocated Photons Product. Results are evaluated using (1) airborne laser altimeter data collected during our ICESat-2 validation campaign over Negribreen, Svalbard, during surge, and (2) high-resolution (0.72 m or 0.86 m) satellite image data from Planet SkySat acquired over Ilulissat Ice Stream (Jakobshavn Isbræ), Greenland. Using DDA-ice analysis, ICESat-2 data allow discrimination of ice-surface types from surging glaciers (Negribreen) and continuously fast-moving and accelerating glaciers (Jakobshavn Isbræ) based on morphological characteristics.