Flat Map Failover is a tool for using individual images to fill in gaps in a map that exist due to lack of overlap. It is most applicable when mapping trees or water.
Flat Maps do not rely on matching features from a bunch of different angles to give an answer the way photogrammetry does. Flat Maps use the aircraft and camera's pointing angles and combine that with the camera's sensor and lens parameters to find out where the images lie on the terrain to provide a quick and dirty output that is used to fill in the gaps.
Starting in 2021 (because it just has to be better than 2020, right?) Maps Made Easy offers standalone processing of Flat Maps and provides the use of Flat Maps to patch areas of normal 3D maps when insufficient overlap is available.
Only the web map gets the patched results. The TIF for the original data and the -patch version of it are available to download separately. If you don't like the results in the web maps you can just trim it out.
Mapping over trees and water is super hard to do properly. That is why they are specifically warned against in the Data Collection guidelines that are agreed to at the time of upload. It is possible to do it but due to the complexity and changing nature of the scene it tend to be problematic.
We usually recommend trying to fix the issue with lots of overlap (80+%). But even then there are no guarantees. Maps Made Easy's photogrammetry engine is optimized in such a way that if it can't give a good answer it won't give one. That is fine (and often preferred by some users) but there are other times when you just need something.
This is where Flat Maps come in. A Flat Map is called that because it does not provide any 3D outputs.
Treed area to the NE did not turn out.
Patched result with Flat Map Failover. Note that elevation layers are not generated.
To enable this feature check the "Flat Map Failover" box in the Output Options on Step 2 of the upload workflow.