Orthomosaic Image and Digital Surface Model for the Swan Lake Drained Lake Basin (MP64) Beaver Dams, Seward Peninsula, Alaska, 03 August 2021

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 03 August 2021 at the Swan Lake Drained Lake Basin, MP64, site on the Seward Peninsula, Alaska. 757 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 110 hectares (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. 4.6.4) 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 centimeters (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涌现》研究项目聚焦于在苔原海狸池塘设立野外监测点位，以探究海狸生态工程活动对水文系统与永久冻土的影响。本研究采用无人机采集基线数据，并长期追踪海狸水坝建造与池塘演化过程。本数据集包含2021年8月3日于阿拉斯加州苏华德半岛MP64点位天鹅湖排干湖盆地开展的无人机测绘所生成的正射影像镶嵌图（orthomosaic）与数字表面模型（DSM）。本次测绘共采集757张数码影像，搭载设备为集成DJI D-RTK 2移动基站的大疆精灵4实时动态差分（DJI P4RTK）四旋翼无人机。测绘区域总面积约为110公顷（ha）。无人机飞行高度设定为地面以上120米（agl），飞行速度区间为8至9米/秒（m/s）。相机拍摄角度固定为90度，即垂直向下拍摄。本次任务的航向重叠度与旁向重叠度分别设置为80%与70%。所有影像均通过Pix4D Mapper软件（v.4.6.4），采用标准三维地图工作流与精准地理定位及姿态校准方法完成处理，最终生成空间分辨率分别为5厘米（cm）与10厘米（cm）的正射影像镶嵌图与数字表面模型。需注意，水体区域提取的高程信息存在噪声，无法反映该类地物的实际表面高程。本次任务采用徕卡Viva差分全球定位系统（GPS）布设地面控制点，所有数据均经后处理，采用WGS84坐标系UTM北纬3带，以椭球高（米）为基准单位。