Kruse, Stefan; Enguehard, Léa; Juday, Glenn; Santosh, Panda; Badola, Anushree; Broers, Jakob; Farkas, Luca; Schladebach, Jacob; Hao, Kunyan; Jackisch, Robert; Döpper, Veronika; Heim, Birgit (2025): Point clouds with ground point classification and individual tree segmentation of 28 northern boreal forest and tundra sites from UAV-based lidar surveys in western and central parts of Alaska in 2024 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.980757

This data set presents LiDAR 3D point clouds with centimetre precision, colored by a RGB camera module. It is a collection of processed point clouds that were collected by a UAV-based laser scanner (YellowScan Mapper). The region covered is part of the Boreal Forest and the Tundra-Taiga Ecotone (TTE). The aim is to map the forest structure and in particular to segment individual trees. This allows structural and biophysical information to be derived on forest condition, stand structure, topography, morphology, disturbance (wildfire, thaw slumps, wind events), thermokarst lakeshore interfaces, etc. The fieldwork was planned and carried out by researchers from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and the University of Alaska Fairbanks (UAF). It took place in the summer of 2024, from 18 June to 17 July. The study area covers boreal forests in different bio-climatic regions and revisits sites established in 2023 and adds more sites. Additionally, the Tundra-Taiga Ecotone was sampled at the Seward Peninsula from the westernmost forests in Alaska close to the settlement of Council and towards Nome. At a multitude of sites, we pre-selected locations based on satellite data. At each site, transects at least 50 m wide and 500 m long were flown in a grid of parallel flight lines 20 m apart. At the ground level, one or, in rare cases, multiple 30-metre-diameter plots were inventoried as ground reference data. The recordings were made at an altitude of 70 m above ground liftoff at a speed of 5 m/s, as recommended by the manufacturer. Before each flight, a GPS base station was set up to collect data for later geographic correction. The raw data processing steps involved correcting the flight trajectories in POSPAC PPTX, flight strip alignment in software YellowScan CloudStation, and colorization with RGB module picture data. The subsequent processing and metadata collection in PC2RCHIVE includes (i) ground classification, (ii) creating Digital Terrain Model (DTM), Digital Surface Model (DSM) and Canopy Height Model (CHM), (ii) tree segmentation, (iv) generating maps, and (v) user provided metadata and relevant information from the data processing are summarized in tables.

Cloth-Simulation-Filter parameters: Classification threshold (m) is the maximum distance between the cloth and a point to be classified as ground (Values used: 0.1/0.2/0.3). Cloth resolution (m) sets the cloth's cell size and is set to a value that ensures flexibility for following the micro-topography, while not being smaller than the inner diameter of the high, hollow vegetation bodies (Values used: 0.1/0.2). Rigidness is the first order stiffness of the cloth (Values used: 1 - flat scenes, 2 - minor relief, 3 - steep slopes).

Data comment on point clouds/.las-file: The point clouds are provided in data format LAS (v1.2 format 3). It contains the RGB information if available. Further, the scalar fields are: (1) intensity, (2) return number of the points, (3) number of returns for the point, (4) classification, either 0 which is aboveground or 2 wich is ground, (5) scan angle rank, (7) point source ID, which is the flight strip, (8) GPS time, and, (9) treeID for the "..._treesonly"-files, which contains unique integer IDs for each segmented tree.

This work was funded by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, for the expedition AK-Land_2024_Beringia North American Forest Change. Additional funding for equipment was provided by the Potsdamer InnoLab für Arktisforschung grant no. F221-08-AWI/001/002, namely the Brandenburg Ministry for Science, Research and Culture. This project has been supported by the DataHub Information Infrastructure funds, projects BorFIT and PC2RCHIVE.

The fieldwork close to Fairbanks was made possible by support from Glenn P. Juday at the University of Fairbanks (UAF). We thank Roy Walluk and his family for their great support to realize the fieldwork leg at the Seward Peninsula.