Geolocated sea-ice or snow surface elevation point cloud segments from helicopter-borne laser scanner during the MOSAiC expedition flight 20200818_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，用于表征海冰或积雪表面高程的时空演化特征，可用于分析海冰干舷、表面粗糙度，以及表面特征的尺寸与空间分布等海冰状态参数。该表面高程数据以DTU21平均海平面高度为参考基准，且未针对数据采集过程中的海冰漂移效应进行校正。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（对应标识符：hdl:10013/sensor.7ebb63c3-dc3b-4f0f-9ca5-f1c6e5462a31 与 hdl:10013/sensor.7a931b33-72ca-46d0-b623-156836ac9550），采集时段为2019年9月至2020年10月，飞行航线覆盖MOSAiC北极漂流科考航线，从拉普捷夫海北部出发，横穿北冰洋中部，最终指向弗拉姆海峡。此次飞行任务包含两种作业尺度：一是小范围飞行，以中央观测站为核心区域，采用约5×5km的网格飞行模式；二是大范围飞行，在距离RV极星号（RV Polarstern）数十公里范围内开展三角形航线或断面航线飞行。点云数据以沿轨5分钟片段的形式存储，采用自定义二进制格式；配套提供基于Python的解析工具（集成于awi-als-toolbox，访问地址：https://github.com/awi-als-toolbox/awi-als-toolbox），同时还提供对应的元数据JSON文件与航线快速预览PNG图像。该点云数据包含以下变量：参考DTU平均海平面高度的表面高程、表面反射率，以及回波宽度。北纬85°以北区域的退化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进行校正。