Geolocated sea-ice or snow surface elevation point cloud segments from helicopter-borne laser scanner during the MOSAiC expedition flight 20200423_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.

本数据集提供高分辨率地理定位点云数据，用于测绘海冰或雪面高程，以表征海冰状态的时空演化特征，涵盖干舷、表面粗糙度，以及表面特征的尺寸与空间分布。该表面高程数据以DTU21平均海平面为基准，采集过程中未针对海冰漂移进行校正。数据由搭载于直升机的近红外线扫描Riegl VQ-580机载激光扫描仪（hdl:10013/sensor.7ebb63c3-dc3b-4f0f-9ca5-f1c6e5462a31 与 hdl:10013/sensor.7a931b33-72ca-46d0-b623-156836ac9550）采集，采集时段为2019年9月至2020年10月，沿MOSAiC漂流科考航线从拉普捷夫海北部横跨北极中部，向弗拉姆海峡方向推进。飞行作业分为两种模式：小范围作业采用约5×5km的网格航线，主要覆盖中心观测站点；大范围作业的航线距离极星号（RV Polarstern）科考船数十公里，采用三角航线或断面测线模式。点云数据以5分钟沿轨分段的自定义二进制格式存储，我们通过awi-als-toolbox（https://github.com/awi-als-toolbox/awi-als-toolbox）提供了基于Python的解析工具，配套相关元数据JSON文件与线扫描快速预览PNG文件。点云数据包含三类变量：以DTU平均海平面为基准的表面高程、表面反射率与回波宽度。北纬85°以北区域的质量不佳的GPS高程数据可能导致沿轨表面高程出现起伏，本数据产品未针对该类起伏开展校正。