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Sun Hotspot Issue?

Mission was flown mid-morning, conditions were mainly sunny. This is the second time collecting data from this area. Looks like sun hotspots, but I was well outside the warning period. I suspect it is causing issues because of the dead trees...maybe the high contrast between green trees and white trees? Has anyone else experienced this? How can I work around it to get a quality mosaic from my dataset? For information sake - 406 images over ~20 hectares, 90m AGL, 80% overlap.

Will Byman

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Another thing I just noticed that is more likely the cause... You may have set it to collect overlap at 80%, but that value is only valid on the ground, not at the tops of the trees. 

Your Overlap Report is not all dark blue in the area that did turn out like it would if 80% overlap had been achieved. This looks more like 70% with the light blues and greens between the passes:

Use the Ground Offset feature to collect the overlap you are trying to get up at the plane of the tops of the trees. If your trees are 30 meters high, raise that offset up 30 meters so the tops of the tress are getting 80% overlap. 

https://support.dronesmadeeasy.com/hc/en-us/articles/209895406-Ground-Offset

 

Zane
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I flew the harvest block to the south immediately after the area discussed above with the same settings and it turned out great.

Will Byman 0 votes
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Trees are tricky, man. More people have trouble mapping trees than any other target 10 to 1. You need to use AT LEAST 80% overlap. Sometimes 85% overlap is the safest thing to do but even then lighting changes can cause issues.

It looks like the areas are getting filled in with the Flat Map Failover which at least gives you something to work with. 

I wouldn't say that is a sun hotspot issue but there is definitely something going on with the lighting which is why it isn't turning out OK. The second map turned out better because it has a lot more open area that is less complicated.

Hard sunlight and trees make for a really complicated scene. The presence of shadows essentially doubles the complexity and the shadows move with every minute that passes. You definitely want to make sure there is not motion in the branches from wind. Sometimes mapping on an overcast day is better because it is more consistent and less complicated. 

Also, orient your passes the short way across the area. This minimizes the amount of time that passes between adjacent views. 

 

Zane 0 votes
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