Hancock Steven, McGrath Ciara, Lowe Christopher, Davenport Ian, Woodhouse Iain
School of Geosciences, University of Edinburgh, Crew Building, Edinburgh EH9 3FF, UK.
Applied Space Technology Laboratory (ApSTL), Department of Electronic and Electrical Engineering, University of Strathclyde, 204 George St, Glasgow G1 1XW, UK.
R Soc Open Sci. 2021 Dec 1;8(12):211166. doi: 10.1098/rsos.211166. eCollection 2021 Dec.
Lidar is the optimum technology for measuring bare-Earth elevation beneath, and the structure of, vegetation. Consequently, airborne laser scanning (ALS) is widely employed for use in a range of applications. However, ALS is not available globally nor frequently updated due to its high cost per unit area. Spaceborne lidar can map globally but energy requirements limit existing spaceborne lidars to sparse sampling missions, unsuitable for many common ALS applications. This paper derives the equations to calculate the coverage a lidar satellite could achieve for a given set of characteristics (released open-source), then uses a cloud map to determine the number of satellites needed to achieve continuous, global coverage within a certain time-frame. Using the characteristics of existing in-orbit technology, a single lidar satellite could have a continuous swath width of 300 m when producing a 30 m resolution map. Consequently, 12 satellites would be needed to produce a continuous map every 5 years, increasing to 418 satellites for 5 m resolution. Building 12 of the currently in-orbit lidar systems is likely to be prohibitively expensive and so the potential of technological developments to lower the cost of a global lidar system (GLS) are discussed. Once these technologies achieve a sufficient readiness level, a GLS could be cost-effectively realized.
激光雷达是测量植被下方裸地高程及其结构的最佳技术。因此，机载激光扫描（ALS）被广泛应用于一系列领域。然而，由于其单位面积成本高昂，ALS在全球范围内并不普及，更新也不频繁。星载激光雷达可以进行全球测绘，但能量需求限制了现有的星载激光雷达只能进行稀疏采样任务，不适用于许多常见的ALS应用。本文推导了用于计算给定特性集的激光雷达卫星所能实现的覆盖范围的方程（已开源），然后使用云图来确定在特定时间范围内实现连续全球覆盖所需的卫星数量。利用现有在轨技术的特性，当制作30米分辨率地图时，单个激光雷达卫星的连续扫描宽度可达300米。因此，每5年制作一幅连续地图需要12颗卫星，对于5米分辨率则需要增加到418颗卫星。建造12个当前在轨的激光雷达系统可能成本过高，因此讨论了技术发展降低全球激光雷达系统（GLS）成本的潜力。一旦这些技术达到足够的成熟度水平，就可以经济高效地实现全球激光雷达系统。
