(2021-10) Comprehensive evaluation of the ICESat-2 ATL08 terrain product (对ICESat - 2 ATL08地形产品进行综合评估)

💡 Meta Data

📜 研究核心

Tips: 做了什么，解决了什么问题，创新点与不足？

“The evaluation is carried out in terms of data specification, survey marks, land cover, season and time (day or night) of acquisition, incidence angle, and terrain slope.”数据规格、测量标志、土地覆盖、采集季节和时间、入射角、地形坡度的综合评价。

ATL08产品在地形坡度或入射角较大的区域更容易低估地形高度，而在地形被茂密的树冠覆盖的区域，地形高度会被高估。

“The ATL08 height errors are further modeled as a function of laser incidence angle and canopy coverage.” ATL08 高度误差进一步建模为激光入射角和冠层覆盖范围的函数。

平原：0.2m；山地：2m

“the majority of ATL08 segments are not useful for terrain extraction.” 大多数 ATL08 段对于地形提取没有用处。

“seasonal variation of terrain height error can be as high as 0.8 m, while the impact of acquisition time is less than 0.3 m.” 地形高度误差的季节变化可高达0.8 m，而采集时间的影响小于0.3 m。

⚙️ 内容

“As a follow-on of the ICESat laser altimetry mission, NASA launched ICESat-2 mission on September 15, 2018 primarily to measure changes in land ice elevation and sea-ice freeboard, and to enable the determination of vegetation canopy height” 作为 ICESat 激光测高任务的后续任务，NASA 于 2018 年 9 月 15 日启动了 ICESat-2 任务，主要测量陆地冰高程和海冰干舷的变化，并确定全球植被冠层高度。

“This configuration allows the measurement of the surface slope in both along and across track directions with a single pass and the measurement of height change from any two passes over the same site [5].” 这种配置（三对强弱不等的光束）允许单次测量沿轨道方向和跨轨道方向的表面坡度，并测量同一地点上任意两次通过的高度变化[5]。

• 1B产品：ATL02 “provides the ATLAS time of flight, ATLAS housekeeping data, and other data necessary for science data processing.” 提供 ATLAS 飞行时间、ATLAS 内务数据以及科学数据处理所需的其他数据。
• 2A产品：ATL03 “latitude, longitude, and ellipsoidal height” 纬度、经度和椭球高度

• 更高级别(3A): “glacier and ice sheet height, sea ice freeboard, vegetation canopy height, ocean surface topography, and inland water body height” 冰川和冰盖高度、海冰干舷、植被冠层高度、海洋表面地形和内陆水体高度

  • ATL08：“valuable terrain (ground surface including buildings) and canopy height” 全球有价值的地形（包括建筑物的地面）和树冠高度

    • “provides height information at a fixed step size of 100m”以 100m 的固定步长提供高度信息
    • “the canopy height (h_canopy)” 冠层高度
    • “terrain height” 地形高度

高程真值来源：

“The U.S. Geological Survey (USGS) 3DEP DEM [21] is regarded as the primary reference elevation.” (Tian 和 Shan, 2021, p. 3) 美国地质调查局 (USGS) 3DEP DEM 被视为主要参考高程。

💡 创新点

研究对象扩充，研究范围扩大，不局限于冰川，平原+山地，；

• “canopy coverage, number of ground photons within each 100-m segment, topography, incidence angle, land cover, season, and data acquisition time.” (Tian 和 Shan, 2021, p. 3) 冠层覆盖范围、每 100 米段内的地面光子数量、地形、入射角、土地覆盖、季节和数据采集时间。

🧩 不足

🔁 研究内容

💧 数据

最适合的地形高度 (h_te_bestfit) 和插值高度 (h_te_interp)

“This initial evaluation confirms the finding with simulated ICESat2 data by Neuenschwander and Pitts in 2019 [7] that the h_te_bestfit is slightly better than the h_te_interp. As such, we will only evaluate the h_te_bestfit in the ATL08 product thereafter.” (Tian 和 Shan, 2021, p. 6) 这一初步评估证实了 Neuenschwander 和 Pitts 在 2019 年 [7] 模拟 ICESat2 数据的发现，即 h_te_bestfit 略优于 h_te_interp。因此，此后我们将仅评估 ATL08 产品中的 h_te_bestfit。

👩🏻‍💻 方法

🔬 实验

📜 结论

“It is shown that the overall uncertainty (standard deviation and mean combined) of height errors increases as the canopy coverage increases.” 结果表明，高度误差的总体不确定性（标准差和平均值组合）随着冠层覆盖度的增加而增加。

🤔 个人总结

Tips: 你对哪些内容产生了疑问，你认为可以如何改进？

🙋‍♀️ 重点记录

“Produced from lidar, ATL08 would overestimate the terrain height referred to survey marks. This overestimation is mainly caused by the mechanism of lidar.” ATL08 由激光雷达产生，会高估测量标记所指的地形高度。这种高估主要是由激光雷达的机制造成的。

“Furthermore, it should be kept in mind that the terrain height provided by ATL08 product is the elevation of ground surface including the building height.” 此外，应记住，ATL08产品提供的地形高度是地表标高，包括建筑物高度。

📌 待解决

💭 思考启发

如何排除建筑物高度与植被高度获取真实地形高度

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