Metashape supports powerlines detection: the algorithm uses aligned images to detect powerlines. This tool is available only in Agisoft Metashape Professional edition.
General recommendations for shooting
Below are our general recommendations for getting better results:
- Photo capturing scenario for powerlines should include at least 3 lines of drone flights with side overlap not less than 60%, and forward overlap not less than 80%.
- For the scenario with 3 lines of drone flights, it is recommended that the line in the middle is captured with nadir direction, while the remaining two lines are captured at a slight angle towards the center (to ensure that the powerlines to be detected take the great part on each image).
- The resolution of images must be good enough to ensure that each separate wire is about 2 pixels wide on the image.
- If there are other linear objects on the images: such as roads or fields with bright sowing rows, then the algorithm can determine such objects as wires (see the left image below). In this case, manual correction is recommended: the incorrectly identified lines can be easily removed (see the right image below).
Photos should be aligned before the powerlines detection procedure can be run. Select Align Photos command from Workflow menu. The recommended parameters for alignment are presented on the image below:
When the photos are aligned select the Detect Powerlines command from the Tools menu and run it with default parameters as presented on the image below:
The meaning of the parameters in the Detect Powerlines dialog:
- Use model for visibility checks - helps to reconstruct more powerlines in scenes with difficult geometry where wires on images are occluded by buildings, constructions, trees, etc. This option can be activated only if a 3D model (Mesh) had been generated for the project.
- Min altitude from DEM (m) - set this parameter to exclude road marking, fences, and other liner objects that are not wired. This option requires DEM to be generated before the powerlines detection procedure.
Additionally the following advanced parameters can be adjusted:
- Tolerance (m) - specify the tolerance for the maximum deviation in meters from the mathematically calculated ideal wire model.
- Maximum number of vertices per line - polylines that correspond to the detected wires can include an excessive number of vertices. To limit the number of vertices specify the desired maximum number of vertices per line. The parameter value 0 (zero) does not apply the limitation to the number of vertices.
Three shape layers will be created once the procedure is executed.
Each layer contains the detected powerlines. The first layer contains all of the liner structures detected on the images (the parameters set on the previous stage are applied). For each following layer, a step-by-step filtering algorithm is applied. You may choose to use the results of the automated filtering mechanism (2nd or 3rd layer) or disable the 2nd and 3rd layers and manually filter the 1st layer.
Detected powerlines will be saved as 3D polylines in one or more shape layers. To export powerlines select File > Export > Export Shape.
See whitepaper by MicaSense "Powerline Inspections and Detection of Vegetation Hazards" to learn about projects where Powerline detection tool is used in combination with multispectral datahttps://share.hsforms.com/1rVZxXCaOSwW6mV67X-1Q9w3vejo