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》项目（Emergence of beavers as ecosystem engineers in the New Arctic project）以苔原（tundra）海狸池塘为野外研究样地，旨在探究海狸的生态工程作用对水文系统与多年冻土的影响。该项目采用无人机（drone）采集基线数据，并长期追踪海狸筑坝活动与池塘的动态演化过程。本数据集包含2021年8月3日于阿拉斯加苏厄德半岛MP64号天鹅湖排水湖盆（Swan Lake Drained Lake Basin）样地开展无人机航测所获取的正射影像镶嵌图（orthomosaic）与数字表面模型（digital surface model, DSM）。本次航测使用大疆精灵4实时动态定位（DJI Phantom 4 Real-Time Kinematic, DJI P4RTK）四旋翼无人机，搭配大疆D-RTK 2移动基站（DJI D-RTK 2 Mobile Base Station），共采集757张数码影像。航测覆盖区域面积约110公顷（hectare, ha）。无人机飞行高度设置为距地面120米（above ground level, agl），飞行速度介于8~9米/秒（meters/second, m/s）之间。相机朝向固定为90度天底视角（即垂直向下拍摄）。本次航测的沿航线重叠度与跨航线重叠度分别设定为80%与70%。所有影像均通过Pix4D Mapper（v.4.6.4）软件，采用标准三维地图处理流程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（centimeter, cm）与10厘米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真实表面高程。本次航测采用徕卡Viva差分全球定位系统（Leica Viva differential global positioning system, GPS）作为地面控制点，并将所有数据后处理至WGS84坐标系下的UTM北3带，采用椭球高（Ellipsoid Heights），单位为米。