Multispectral Orthomosaic Image for the Swan Lake Creek Beaver Dams, Seward Peninsula, Alaska, 02 August 2023

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 a multispectral orthomosaic derived from drone surveys on 02 August 2023 at the Swan Lake Creek site on the Seward Peninsula, Alaska. 828 digital images from five spectral bands 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 38 hectares (ha). The drone system was flown at 120 meters (m) above ground level (agl) and images were captured using the hover and capture at point mode. 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. 4.8.4) using the standard 3D Maps workflow and the accurate geolocation and orientation calibration method to produce the multispectral orthophoto mosaic at a spatial resolution of 10 centimeters (cm). Images of a MicaSense calibrated reflectance panel were used for radiometric processing and calibration of each spectral band in the Index Calculator in Pix4D. 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.

《新北极地区海狸作为生态系统工程师的涌现》项目聚焦于在苔原（tundra）海狸池塘设立野外站点，以探究海狸生态工程活动对水文与多年冻土（permafrost）的影响。本项目借助无人机采集基线数据，并长期追踪海狸筑坝行为与池塘演化过程。本数据集包含2023年8月2日于阿拉斯加苏华德半岛天鹅湖溪（Swan Lake Creek）站点开展无人机航测所生成的多光谱正射影像镶嵌图（multispectral orthomosaic）。本次航测采用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5个光谱波段的数码影像828张。测绘区域面积约38公顷（hectare, ha）。无人机飞行高度设置为距地面120米（meter, m），采用悬停定点拍摄模式采集影像，相机朝向设为90度垂直向下。本次航测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（v.4.8.4）软件，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进行处理，生成空间分辨率为10厘米（centimeter, cm）的多光谱正射影像镶嵌图。本研究利用MicaSense校准反射面板的影像，在Pix4D的指数计算器（Index Calculator）中完成各光谱波段的辐射处理与定标。本次航测以徕卡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 Zone 3 North坐标系。