Merged grids of sea-ice or snow freeboard from helicopter-borne laser scanner during the MOSAiC expedition flight 20200907_01, version 1

This data set is a higher-processing-level version of Gridded segments of sea-ice or snow surface elevation and freeboard from helicopter-borne laser scanner during the MOSAiC expedition, version 1 (Hutter et al., 2022; doi:10.1594/PANGAEA.950339), where the individual 30-second segments of the small scale grid flights have been combined into merged grids. 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 merged data are stored in netCDF and geotiff format. 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. For the flights with degraded GPS altitude quality, we provide only a freeboard estimate. The merged grids include all data variables of the gridded 30-s segments: surface elevation, freeboard (estimate), freeboard uncertainty, estimated sea surface height, surface reflectance, echo width, and number of points used in the interpolation. Also the calculated elevation offset correction term is provided for each flight as a csv file.

本数据集为MOSAiC科考航次期间直升机搭载式激光扫描仪采集的海冰/雪面高程及干舷（freeboard）格网分段数据的更高处理级别版本（版本1，Hutter等，2022；DOI：10.1594/PANGAEA.950339），该版本将小型格网飞行任务的单条30秒分段数据合并为统一格网数据集。
数据采集采用搭载于直升机的线扫描近红外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）完成，采集航线随MOSAiC科考浮冰漂移，从拉普捷夫海北部出发，横穿北冰洋中部，最终驶向弗拉姆海峡，采集时段为2019年9月至2020年10月。
合并后的数据以网络通用数据格式（netCDF）与地理标记图像文件格式（GeoTIFF）存储。
数据处理阶段采用极星号（RV Polarstern）科考船的位置与航向数据完成漂移校正，并利用重叠分段数据对高程偏移量进行校正，以解决北纬85°以上区域GPS高程数据质量下降的问题。
针对GPS高程数据质量不佳的飞行任务，本数据集仅提供干舷估算值。
合并格网数据集包含原始30秒格网分段的全部数据变量：表面高程、干舷估算值、干舷不确定性、估算海面高度、表面反射率、回波宽度以及插值所用的点数。
此外，针对每一次飞行任务计算得到的高程偏移校正项，均以逗号分隔值（CSV）文件形式提供。