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Author Topic: Minimum percent overlap  (Read 2216 times)

rossnixon

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Minimum percent overlap
« on: September 08, 2020, 01:21:08 AM »
I understand that a 60% or higher overlap is required for aerial photos in a run.
If there are several parallel runs, what is the minimum percent overlap with the adjacent runs?
These will all need to align in Metashape and be processed in one chunk.

Thanks.

Arie

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Re: Minimum percent overlap
« Reply #1 on: September 09, 2020, 01:34:10 PM »
Hi,
usually it's stated that the overlap for aerial projects should be 80% forwards and 60% sidewards. Some even do a 80% and 80% overlap.
You can get away with less than that, but your accuracy can suffer quite a bit and it's not fun trying to correct that.
Cheers!
« Last Edit: September 09, 2020, 01:37:11 PM by Arie »

Darko

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Re: Minimum percent overlap
« Reply #2 on: September 10, 2020, 09:52:53 AM »
Just to produce the Orthophoto, even 30% is sufficient. Not good for 3D models, for that you need 80% both ways. Of course, that stands for the regular lenses, not too wide (20-25 mm on Sony A6000).

Arie

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Re: Minimum percent overlap
« Reply #3 on: September 10, 2020, 12:27:51 PM »
With 30% overlap how will you create a DEM/ Mesh for proper orthorectification?

Darko

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Re: Minimum percent overlap
« Reply #4 on: September 18, 2020, 11:28:02 AM »
It works..
Demand for the photogrammetry was 60% longitudal and 25% side overlap before that mumbo-jumbo digital photogrammetry that we have today. That's from my old books I've learned that from. To get the 3D solution you need the same point on at least 2 photos. You have that all in one flight strip only, so, why would you need side overlap at all? It is needed since the strips have to join the same model and 30% is sufficient. Try it. Take some older data with more overlap and process every odd flight line. You'll get similar results.

Best,
Darko

Arie

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Re: Minimum percent overlap
« Reply #5 on: September 18, 2020, 11:37:56 AM »
You fail to mention, that this is done with highly specialized equipment, such as metric cameras....
One needs a accurate DEM to compute an accurate orthoimage. With consumer-grade equipment you will not be able to achieve that with a 60% forward and 25% sideward overlap.
Cheers!

Darko

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Re: Minimum percent overlap
« Reply #6 on: September 18, 2020, 12:08:01 PM »
Hi,
My equipment is PPK solution with Sony A6000, 25mm fix focus, fix aperture, but, CALIBRATED lens. My orthophotos have good accuracy of 5 cm or better (5 cm ground resolution). Try it for yourself, just reprocess some old job and take every second line. You'll be surprised.
Best,
Darko