How to map and measure Pole and Tower Structures

 
Important: Pole structures such as power lines are difficult to model as they are very thin and tall structures. Besides, this kind of structures is often made of reflective materials, and therefore they often appear white in the images and very few keypoints can be detected on them.

 

There are 2 main possibilities to map pole and / or tower structures:

 

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.

 
Information: For more information about how to draw a polyline: How to draw a Polyline in the rayCloud.

Using a fisheye camera may help to capture the images because of the wide field of view of the lens.

 

(Recommended) Images taken from the side (oblique)

It is recommended to fly close to the structure and as flight plan, there are several possibilities:

  • Turning several times around it while changing the altitude, following a spiral.
  • Making several circles around the object at different altitudes.
  • Making several vertical length 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 on images which make them easier to match and it provides a better model. For more information:

 

Video Example

 

Video Tutorial

 

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6 comments

  • Alessandro Bedin

    Hello, I have to map the exteriors of an offshore platform, then in the background instead of the ground there is water. Can the water cause any problem when building the orthomosaic like the sky does? 

    Edited by Alessandro Bedin
  • Kapil (Pix4D)
     

    Hi Alessandro,

    Images that capture only water might not be calibrated (optimize the internal and external orientation of the camera). The reason is that it is very hard to find keypoints on water surfaces (water is very uniform). Even if keypoints are found, it is very hard to match them between images, as these points are not static. This will have an issue as you are expecting. 

    However, you can also edit the unwanted point cloud to clean it in case of any issue. For more information, I would recommend you to go through our support article on How to edit the point cloud in the rayCloud.

    Thanks,

     
  • Dennis Smith

    Is it possible at all with Pix4D to capture distribution and transmission conductors using photogrammetry? I understand it is difficult but impossible? 

  • Dan Harmening

    I too am very interested in mapping the Conductors in Pix4D point cloud.  I am waiting on my data from a large file and will apply the information gathered.  Any further details would be great!

  • Holden (Pix4D)

    Hi Dan and Dennis. This is possible depending on the level of detail desired but requires very high overlap and advanced workflow knowledge to accomplish. You can reference the principals above in order to give the best chance of success and share your results on the community to help others.

  • Jackson Miller

    Hello Holden!  Im happy to know that this is possible! Can you give us some pointers on the workflow? Is there someone with Pix4D who has had success with this who might be able to help us out?  It looks like we should be able to add tie points in the images on the conductors and that will generate point cloud for those points. Is that right? 

     

    Dan, have you had any success with the data you were waiting on? 

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