Geolocated sea-ice or snow surface elevation point cloud segments from helicopter-borne laser scanner during the MOSAiC expedition flight 20200123_02, version 1

This data set provides high-resolution geolocated point clouds of sea-ice or snow surface elevation for mapping temporal and spatial evolution of sea-ice conditions such as freeboard, roughness, or the size and spatial distributions of surface features. The surface elevation data are referenced to the DTU21 mean sea surface height and are not corrected for sea-ice drift during acquisition. The data were collected using a near-infrared, line-scanning Riegl VQ-580 airborne laser scanner (hdl:10013/sensor.7ebb63c3-dc3b-4f0f-9ca5-f1c6e5462a31 & hdl:10013/sensor.7a931b33-72ca-46d0-b623-156836ac9550) mounted in a helicopter along the MOSAiC drift from the north of the Laptev Sea, across the central Arctic Ocean, and towards the Fram Strait from September 2019 to October 2020. The flights are both small scale, ~5x5 km grid patterns mainly over the central observatory, and large scale, few tens of km away from RV Polarstern, triangle patterns, or transects. The point cloud data are stored in 5-min along-track segments in a custom binary format, for which we provide a python-based parsing tool in awi-als-toolbox (https://github.com/awi-als-toolbox/awi-als-toolbox), together with corresponding metadata json and line-shot quicklook png files. The point cloud data includes as variables: surface elevation (referenced to DTU mean sea surface height), surface reflectance, and echo width. The degraded GPS altitude data >85°N may cause undulations in the along-track surface elevations, which are not corrected for in this data product.

本数据集提供海冰或雪面高程的高分辨率地理定位点云（geolocated point clouds），用于刻画海冰状态（如海冰干舷（freeboard）、表面粗糙度，以及地表特征的规模与空间分布）的时空演化特征。该表面高程数据以DTU21平均海面高（DTU21 mean sea surface height）为参考基准，采集过程中未针对海冰漂移（sea-ice drift）进行校正。数据采集采用搭载于直升机的近红外线扫描Riegl VQ-580机载激光扫描仪（near-infrared, line-scanning Riegl VQ-580 airborne laser scanner，hdl:10013/sensor.7ebb63c3-dc3b-4f0f-9ca5-f1c6e5462a31 与 hdl:10013/sensor.7a931b33-72ca-46d0-b623-156836ac9550），沿MOSAiC科考漂移航线采集，覆盖范围从拉普捷夫海（Laptev Sea）北部出发，横穿北极中央海域（central Arctic Ocean），并于2019年9月至2020年10月期间向弗拉姆海峡（Fram Strait）延伸。本次飞行航线分为两类：一类为小尺度航线，即以中央观测站为核心的约5×5km网格模式；另一类为大尺度航线，涵盖距离“极星号（RV Polarstern）”科考船数十公里范围的三角形航线或断面航线。点云数据以5分钟沿轨分段（along-track segments）的形式存储于自定义二进制格式（custom binary format）中，配套提供基于Python的解析工具（python-based parsing tool，托管于awi-als-toolbox仓库：https://github.com/awi-als-toolbox/awi-als-toolbox），同时包含对应的元数据JSON（metadata json）文件与线扫描快速预览PNG（line-shot quicklook png）文件。该点云数据包含以下变量：以DTU平均海面高为参考的表面高程、表面反射率（surface reflectance）以及回波宽度（echo width）。北纬85度以上区域的退化GPS高程数据（GPS altitude data >85°N）可能导致沿轨表面高程出现起伏偏差（undulations），本数据产品未针对该偏差进行校正。