Gridded segments of sea-ice or snow surface elevation and freeboard from helicopter-borne laser scanner during the MOSAiC expedition flight 20200711_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干舷（freeboard），并投影至规则0.5米网格中。
数据采集使用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），采集时段为2019年9月至2020年10月，沿MOSAiC科考漂流轨迹从拉普捷夫海北部横穿北冰洋中部，并向弗拉姆海峡方向推进。
飞行作业分为两类：一类为小尺度作业，以约5×5公里的网格模式为主，覆盖中部观测站点区域；另一类为大尺度作业，在距离极星号（RV Polarstern）科考船数十公里外开展，采用三角网格模式或断面航线模式。
网格化数据以沿轨30秒分段的网络通用数据格式（netCDF）存储。针对小尺度网格飞行作业，利用极星号（RV Polarstern）的位置与航向数据对数据进行漂移校正，并通过重叠分段对高程偏移量进行校正，以解决北纬85°以上区域GPS高程数据质量不佳的问题。
本数据集通过自动识别敞水区点，从表面高程数据中推导出干舷估算值。对于GPS高程数据质量不佳的飞行作业，仅提供干舷估算值（网格模式飞行）或不提供干舷数据（断面航线飞行）。
网格化30秒分段数据包含如下数据变量：表面高程、干舷估算值、干舷不确定性、估算海表高度、表面反射率、回波宽度以及插值所用的点数。此外，数据集还提供检测到的敞水区点列表以及每一次飞行作业的概览图。