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Roof of a building didn't turn out well

Ryan -

It is very common when mapping a large area that contains structures to forget to account for the added height of the building when planning for overlap.

When flying low, it is very easy to forget that areas that are above the ground will get less overlap due to the wide field of view of most aerial cameras.

If you are flying at 50 meters above ground level and there is a building that is 15 meters tall, you are going to have a bad time. This why the Data Collection guidelines recommend flying at least 4-5 times the height of the tallest object. The goal is to limit differences in coverage due to differences in height.

 

Example

The example below shows the overlap being set around 70% so the coverage on the ground is good but the roofs of the structures in the middle get very little coverage. In the case of a shiny metal or featureless roof, this can make it hard to accurately reconstruct. The areas with only 4X overlap ended up being distorted with swirls.

Read more about the effect in the "Elevation Difference Overlap Reduction in Structures" section of the Overlap Reports article.

To keep this from happening, fly higher to limit this effect or use more overlap than is generally needed. Another way to fix this would be to take a few extra pictures to fill in the overlap and include that with the uploaded imagery.

 

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Comments

  • Avatar
    Oyibo VFX

    I have made four maps of my site in Africa. The last three went well. More then one battery. No issues there. So, the last flight of today decided to buy points because we do a large area survey.
    The first kmz image I uploaded to Google went well for over 90%. But the other two kmz files are hardly to see. I have downloaded the jpg file and those are perfect. Just not the kmz on GE.
    I must say there are a lot of trees and vegetation (the reason for the survey.
    For me it's important to put the files in Dropbox so my client have access. But without Google Earth, it has not much use....

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