Map quality issue - overlaps

I just processed another map using the same process I've used successfully in the past, and the overlap report is showing no overlap for a large part of the mapped area, despite being in the same regular grid as before:

Any suggestions what causes this? Looking at the raw images, they seem fine.

Nick Johnson May 18, 2022 21:53

Official comment

We are sorry to hear you are unhappy with your results. It looks like you got pretty lucky with some of your previous work and it didn't turn out this time.

The overlap is OK but isn't great... We recommend using 75% overlap in the Data Collection guidelines that are agreed to at the time of upload. This looks like about 70% overlap. 80% is recommended for doing work with trees. While the areas you are looking at are not solid trees there is still a lot in the area. 75% overlap corresponds to everything in the area getting 16 looks at it which would make the overlap report be completely dark blue.

We set the defaults in Map Pilot Pro to use 80% overlap because that is usually enough to ensure respectable results.

The Flat Map Failover filled in the areas with the red dots.

Zane May 19, 2022 03:48

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5 comments

I'm using 75% front overlap and 70% side overlap. I can bump them up to 80, but I still don't understand what's going on here. The spacing is the same between all points; why would it claim there's no overlap from the pictures covered by the red dots?

Nick Johnson May 19, 2022 03:50 0 votes

The 70% is likely what is doing it. From the Overlap Report article that is shown when you click on that "What is this?" link:

"A red dot at an imaging location denotes that there was an image that was processed but it did not have sufficient overlap and/or matchable features so it was not included in the output."

Basically the system didn't have enough overlap to match the features in those images so it draws a red dot to tell you it wasn't included in the results.

You can't just use one setting for everything. It is scene dependent. Some content, like trees and the stuff identified in the Data Collection guidelines, requires more overlap.

Using 80% overlap will help overcome other differences that are introduced by exposure differences, flight speed, time of day, lighting conditions, surface reflections and other variations that can affect feature matching.

Zane May 19, 2022 04:14 0 votes

Thanks for the further detail.

I just ran this myself in WebODM, and it got 100% of the area correctly. Any idea why mapsmadeeasy is having trouble with it?

Nick Johnson May 20, 2022 02:54 0 votes

Maps Made Easy is does not use other software and is likely having trouble with this since we recommend the use of at least 75% overlap as noted in the guidelines.

Zane May 20, 2022 05:01 0 votes