Drone topographic survey of a proposed wind farm
Aerial Vision – a drone topographical surveying company particularly experienced in the energy sector, was commissioned to inspect an area in Central Scotland for the proposed development of a wind farm.
The proposed wind farm will comprise four wind turbines with 125-meter tip height, producing 13.2 Megawatts of electricity: enough to supply power to 6398 homes.
The image above shows a detailed topographical survey of the area highlighted in green, which was required for GIS analysis.
The map is shown in low resolution in order to protect the client and keep the site confidential.
Aerial Vision was commissioned to provide a detailed topographic survey of the ridge and surrounding land area.
|Project date||February 2016|
|Project members||Aerial Vision , Geo-4D|
|Project size||11 Hectares|
|Number of images||181|
The site contains a glacial ridge and old quarry with steep vertical faces. The access is from the north of the site and the four turbines are south of the ridge, and thus the access track needs to ascend and descend this ridge and the gradient and curvature of bends must be carefully controlled due to the mass and wheel base of the vehicles transporting the wind turbine components.
Mapping the proposal
As the survey area was small and close to the road, a rotary drone was chosen. The site area under investigation was mapped using a DJI Phantom 3 and a compatible flight control system. A flight plan was created at an altitude of 60 meters from the top of the ridge, which enabled the camera on-board to take images with a 2.6 centimeter ground sampling distance. The flight corridors are close enough to give a 70% image side lap to ensure accurate 3D modeling and representation.
Mapping from images
Geo-4D, a photogrammetric consulting and training company from the UK, provided image processing support, using Pix4Dmapper to generate a precise 3D point cloud from the aerial images. RTK GPS data collected on site was used as ground control points (GCPs) and processed with the image dataset, providing < 5 cm horizontal and < 10 cm vertical accuracies.
From the topographic maps produced, a careful curved route that satisfied the required criteria was able to be chosen to the west of the old quarry.
Outputs produced were: a digital surface model (DSM), digital terrain model (DTM) (obtained by removing the above-ground features such as trees and buildings), and a georeferenced orthomosaic in RGB. The DSM and DTM were down-sampled to a one meter resolution by request and put into a GIS software along with the orthomosaic, allowing the design team to plan the access track.
Why use Pix4Dmapper
Drone photogrammetry produces LiDAR quality analysis results at a fraction of the cost associated with LiDAR. If required, analysis of the results can provide accurate cut and fill volumes in Pix4Dmapper as well as be exported to GIS or CAD software packages for advanced spatial analysis and/or professional charting.
From this model, a rendered ‘fly through’ video was created. This is an .mp4 movie file that can be viewed on pc, mac, tablet, iOS and android platforms, perfect for public exhibitions.