Gridded segments of sea-ice or snow surface elevation and freeboard from helicopter-borne laser scanner during the MOSAiC expedition flight 20191002_01, version 1

This data set is a higher-processing-level version of Geolocated sea-ice or snow surface elevation point clouds from helicopter-borne laser scanner during the MOSAiC expedition, version 1 (Jutila et al., 2022; doi:10.1594/PANGAEA.950509), where the surface elevation point cloud has been converted to freeboard using automatic open water detection scheme and projected onto a regular 0.5-meter grid. 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 gridded data are stored in 30-second along-track segments in netCDF format. For the small scale grid flights, the data are drift corrected using the position and heading data of RV Polarstern and elevation offset corrected using overlapping segments to overcome degraded GPS altitude data >85°N. Open water points are identified to derive a freeboard estimate from the surface elevations. For the flights with degraded GPS altitude quality, we provide only a freeboard estimate (grid pattern flights) or no freeboard (transects). The gridded 30-s segments include as data variables: surface elevation, freeboard (estimate), freeboard uncertainty, estimated sea surface height, surface reflectance, echo width, and number of points used in the interpolation. In addition, list of detected open water points and an overview figure of each flight is provided.

本数据集为MOSAiC科考期间机载直升机激光扫描获取的地理定位海冰/雪面高程点云的高阶处理版本（版本1，Jutila等，2022；doi:10.1594/PANGAEA.950509），其中已通过自动敞水区识别方案将表面高程点云转换为海冰干舷（freeboard），并投影至规则的0.5米网格。本次数据采集采用安装于直升机的近红外线扫描Riegl VQ-580机载激光扫描仪（标识符：hdl:10013/sensor.7ebb63c3-dc3b-4f0f-9ca5-f1c6e5462a31 与 hdl:10013/sensor.7a931b33-72ca-46d0-b623-156836ac9550），于2019年9月至2020年10月期间沿MOSAiC科考漂流轨迹采集，轨迹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。飞行作业包含两种尺度：小尺度作业为约5×5公里的网格模式，主要覆盖中央观测点；大尺度作业则为距离极星号科考船（RV Polarstern）数十公里范围的三角模式或断面航线。网格化数据以沿航迹30秒片段的形式存储，格式为netCDF。针对小尺度网格飞行作业，数据已通过极星号科考船的位置与航向数据进行漂流校正，并通过重叠片段进行高程偏移校正，以解决北纬85°以上区域GPS高程数据退化的问题。通过识别敞水区点云，从表面高程中推导出干舷估算值。对于GPS高程质量退化的飞行任务，我们仅提供干舷估算值（适用于网格模式飞行）或不提供干舷数据（适用于断面航线）。网格化30秒片段包含以下数据变量：表面高程、干舷（估算值）、干舷不确定性、估算海水面高度、表面反射率、回波宽度，以及插值所用的点云数量。此外，本数据集还附带检测到的敞水区点云列表，以及每一次飞行作业的概览图。