Orthomosaic Image and Digital Surface Model for the Swan Lake Drained Lake Basin (MP64) Beaver Dams, Seward Peninsula, Alaska, 12 August 2022

Emergence of beavers as ecosystem engineers in the New Arctic project focuses on establishing field sites at tundra beaver ponds to study the implications of beaver engineering on hydrology and permafrost. Drones are being used to collect baseline data and track beaver dam building and pond evolution over time. This dataset consists of an orthomosaic and digital surface model (DSM) derived from drone surveys on 12 August 2022 at the Swan Lake Drained Lake Basin, MP64, site on the Seward Peninsula, Alaska. 910 digital images were acquired from a DJI Phantom 4 Real-Time Kinematic (DJI P4RTK) quadcopter with a DJI D-RTK 2 Mobile Base Station. The mapped area was around 140 ha. The drone system was flown at 120 meters (m) above ground level (agl) and flight speeds varied from 8-9 meters/second (m/s). The orientation of the camera was set to 90 degrees (i.e. looking straight down). The along-track overlap and across-track overlap of the mission were set at 80% and 70%, respectively. All images were processed in the software Pix4D Mapper (v. 4.7.5) using the standard 3D Maps workflow and the accurate geolocation and orientation calibration method to produce the orthophoto mosaic and digital surface model at spatial resolutions of 5 and 10 centimeter (cm), respectively. Elevation information derived over waterbodies is noisy and does not represent the surface elevation of the feature. A Leica Viva differential global positioning system (GPS) provided ground control for the mission and the data were post-processed to WGS84 UTM Zone 3 North in Ellipsoid Heights (meters).

“新北极地区海狸作为生态系统工程师的崛起”项目聚焦于在苔原海狸池塘设立野外站点，以研究海狸的生态工程活动对水文与永久冻土（permafrost）的影响。研究团队使用无人机采集基础数据，并长期追踪海狸水坝建造与池塘演化过程。本数据集包含2022年8月12日于阿拉斯加苏华德半岛MP64站点天鹅湖排水湖盆开展无人机测绘所生成的正射影像镶嵌图（orthomosaic）与数字表面模型（digital surface model, DSM）。本次测绘采用DJI Phantom 4 实时动态（Real-Time Kinematic, RTK）四旋翼无人机（DJI P4RTK）搭配DJI D-RTK 2移动基站，共采集910张数码影像。测绘区域面积约140公顷。无人机飞行高度设为距地面120米（above ground level, AGL），飞行速度介于8至9米/秒（meters/second, m/s）。相机朝向设置为垂直向下（90度）。本次任务的航向重叠度与旁向重叠度分别为80%与70%。所有影像均通过Pix4D Mapper软件（版本4.7.5），采用标准三维测绘工作流与精准地理定位及姿态校准方法进行处理，分别生成空间分辨率为5厘米（centimeter, cm）与10厘米的正射影像镶嵌图与数字表面模型。水体上方提取的高程信息存在噪声，无法代表该地物的实际地表高程。本次任务采用徕卡Viva差分全球定位系统（differential global positioning system, GPS）作为地面控制点，并将数据后处理至WGS84 UTM第3北带坐标系，采用椭球高（单位：米）。