Case Study: LiDAR and Photogrammetry Power Line Survey
The Challenge: As part of a planning application for a solar farm, we were required to capture approximately 15 km of 220 kV and 110 kV power lines, which were adjacent to the ground survey area.
The ground area where the panels would go was not too challenging, as these were relatively open fields; however, some were heavily vegetated with unharvested crops.
For much of the power line survey area, there was no access to the land. This ruled out traditional survey methods as it would have been very time-consuming to contact and liaise with dozens of landowners. This also posed safety concerns, particularly working near the power lines and navigating the uneven and sometimes hazardous terrain below them.
As can be seen in the video, dense vegetation covered much of the area, which would have hindered access and caused safety concerns.
The Solution: We combined LiDAR and Photogrammetry surveys using drone technology. This was carried out using the DJI Zenmuse L1 and P1 on the Matrice 300 RTK. During processing, we merged and classified the point clouds using 3D Survey, which enabled the extraction of poles, lines, and connectors, allowing engineers to visualise the clearance below the power lines. One of the significant advantages of 3D Survey is that it enables the user to select the exact point in the point cloud using photo support. This enhances the accuracy of CAD extraction, particularly for objects that are thin or difficult to define due to vegetation.
Through the use of Aerial LiDAR, we are about to attain over 300ppm, which is points per metre squared. This is significantly higher than traditional survey methods, resulting in more accurate and detailed terrain definition.
By classifying the point cloud, we can eliminate those classes from the view, allowing you to hide High, Medium and Low vegetation to aid in the CAD linework extraction.
We needed LiDAR because the cable diameter is often too small to be reconstructed accurately through photogrammetry alone. The software often struggles to reconstruct the 220kV transmission tower and power lines. LiDAR, however, does not have this problem, which is one of its many benefits over photogrammetry in this scenario.
The Benefit: Getting access to the land to survey the powerlines would have taken months, and that’s not factoring in the time taken to survey 15km of Power Lines.
Without needing access to the site, we were able to combine the point clouds of the LiDAR and Photogrammetry surveys to capture the position, height, drop, and span of the Overhead Power Lines.
We achieved accuracies of 5-6 cm in the X, Y, and Z axes, without putting anyone in danger, and completed the survey in a fraction of the time it would have taken otherwise.
Not only did we reduce the cost by over 70%, but we also delivered the survey results in less than 15% of the time of a traditional survey of this size
This same survey technique is highly beneficial for vegetation encroachment, distance calculations and overhanging trees. It can be used for the maintenance of not just powerlines but also fibre and telecoms networks, where outages from storm damage cause serious downtime for customers.