Orthomosaic Image and Digital Surface Model for the Swan Lake Creek 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 Creek site on the Seward Peninsula, Alaska. 977 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 60 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. 4.7.5) 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 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》研究项目以苔原海狸池塘为野外研究站点，旨在探究海狸生态工程活动对水文与多年冻土的影响。本研究采用无人机采集基线数据，并长期追踪海狸水坝修筑与池塘演化过程。本数据集包含2022年8月12日于阿拉斯加州苏厄德半岛天鹅湖溪站点无人机测绘获取的正射影像镶嵌图（orthomosaic）与数字表面模型（DSM）。数据采集使用搭载DJI D-RTK 2移动基站的DJI Phantom 4实时动态差分（DJI P4RTK）四旋翼无人机，共获取977张数码影像。测绘区域面积约60公顷（ha）。无人机飞行高度设置为离地120米（agl），飞行速度介于8~9米/秒（m/s）之间。相机拍摄角度设为90°（即垂直向下拍摄）。本次测绘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.4.7.5），采用标准三维地图作业流程及精准地理定位与姿态校准方法进行处理，最终分别生成空间分辨率为5厘米（cm）与10厘米（cm）的正射影像镶嵌图及数字表面模型。需注意，水体区域提取的高程信息存在噪声，无法反映该区域的真实地表高程。本次任务采用徕卡Viva差分全球定位系统（GPS）作为地面控制点，并将数据后处理至WGS84坐标系下的UTM 3N带，采用椭球高（单位：米）。