Ortho view of power lines not lining up

We're using a DJI P1 processed in Metashape to create orthophotos. We're having problems with power lines being disconnected. Fences and other long, straight objects that are on the ground are all fine, it's the power lines that are the issue. Does anyone have any idea what's going on? This is just our first test so no ground control and fully automatic camera settings. I'm going to try manual focus with auto shutter etc. but we've had the same problem with our Phantom 4 and never found a solution.

  • 7
    This happens a lot in orthophotography. You're looking at a 2d representation of a 3d scene, the generating photos are taken from different XYZ locations, then when you align the ground correctly the above ground features appear to lean; your fences are significantly closer to the ground so the distortion isn't much. You need to have your seamlines following the power line and then just hope your drone image is consistent from frame to frame. Seamlines generally follow road/watercourse centres and ridge lines which is why medium/large format is flown with 60% overlap. Mar 27 at 2:48
  • That's an idea I haven't heard before. I'm getting the impression there's no easy fix for this problem. We're interested in the orthophoto for the client, the power lines aren't the focus, it just doesn't look good for the client.
    – GlenS
    Mar 27 at 21:35
  • 2
    If you want to make the power lines straight and contiguous you will need to fly directly above them and adjust the seamlines to give priority. The lean of the power poles is more pronounced due to the low altitude you're flying; at a low altitude you see more of the sides of tall objects than you would flying at a few thousand feet above the terrain. You will see the same effect from very tall trees and buildings, water towers, aerials etc. Mar 28 at 0:54
  • Great answer, thanks. Is there a way to estimate a good minimum altitude for a given feature height?
    – GlenS
    Mar 28 at 8:28
  • 2
    Not that I know of. Usually if you have tall structures you increase the overlap to give you more options for seamlines; Once we did Melbourne CBD at 95% overlap to minimize the leaning, you choose the frame that is closest to perpendicular for each building. It's a lot of work to achieve this and it starts at the flight planning stage; use Google Earth to locate powerlines and tall buildings and plan to do extra runs over these. Don't forget to keep your altitude lower than air traffic, especially in ATC areas, a collision could be deadly. Mar 30 at 0:48


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