This article provides two possibilities to map and measure pole and tower structures, with oblique (recommended) and nadir images.
There are two main possibilities to map pole and/or tower structures:
(Recommended) Images taken from the side (oblique)
It is recommended to fly close to the structure. Regarding the flight plan, there are several possibilities:
- Turning several times around the object of interest while changing the altitude, following a spiral.
- Making several circles around the object at different altitudes.
- Making several vertical lengths from the bottom to the top of the structure at different positions around the object.
In all cases, it is needed to have a very good overlap between images (at least 85% frontal and side overlap).
The camera should have a 45-degree angle pointing to the ground. By pointing the camera to the ground, less sky content is visible in images, which makes them easier to match and provides a better model. For more information:
Images taken from above (nadir)
A very high overlap is required (more than 90%).
If the structure is not fully reconstructed in the rayCloud, it is possible to digitize it by creating polylines and by refining the vertices of the polylines in the images.
Using a fisheye camera may help to capture the images because of the wide field of view of the lens.