At the request of Geoterra Skeye carried out an Aerial Topographic Survey of a large project area for a wind farm development. The area is located in the United Kingdom close to the Scottish border with an area of 2.5 km2. The aim of the survey was to produce a 3D digital Terrain Model and an overview aerial photograph (orthophoto mosaic) of the entire area.
The reason to use an aerial survey using a drone was that with traditional (land) survey techniques less detail can be captured ( 1 height measurement per 10m2) as compared to an aerial survey where 100 points per m2 can be captured. In addition the aerial survey can provide a full overview of the area from the aerial photography.
The project area was located in a former peat bog with difficult access to most of the site. Skeye operated the Trimble UX5-HP fixed wind drone or UAV to acquire aerial images at high resolution. The Trimble UX5-HP is equipped with a L1/L2 GNSS receiver, which means fewer ground control points need to be installed compared to an aerial survey without this technology. Flying took a single day with a second day being used to place ground control points and take extra measurements for the quality control. All ground control points were made using RTK GPS equipment.
The aerial images were processed using photogrammetric software from which all terrain heights could be extracted. From these height observations the points that do not belong to the ground (trees and other structures) were filtered out. The result was an exact 3D representation of the bare earth. In addition all the aerial images were stitched together to create one seamless aerial image corrected for colour differences and terrain heights.