This may or may not help you, but I found good canopy results in a 4 mile road project I performed. I setup the GCP’s and overlap for Corridor Mapping as suggested in https://support.pix4d.com/hc/en-us/articles/202557459.
I used 90% + Frontal overlap since the minimum suggested is 85% for a corridor.
After Flying down the center-line, I decided to fly parallel paths over both road ROW’s, giving me 3 flight paths instead of the originally planned 1 path. The Sidelap was 70 - 75%.
Even though I was not interested in the Canopy, Pix4d did a great job modeling the trees. Much better than I normally see in my work.
Of course ground contours matched the LiDAR data I had for a portion of that project, due to using Survey Grade Ground Control Points.
You may want to try 90% Frontal, 80% Side overlap, and enough Ground Control Points as these will substantially help the reconstruction. If you are not satisfied, you will need to fly lower for a better GSD. Since my final output is normally Ortho’s, I generally fly for a GSD of 1-2 cm.
I usually end up collecting way too much data in the field, but I’ve found that’s easier and cheaper than having to go back and re-fly a portion of any project. Hard Drives are cheap and it’s easy to adjust the resolution of the final deliverable. We can always reduce final output resolution in the office, but cant increase it. That’s why I changed my mind in the field and flew 3 flight paths instead of the One Path I had planned for in the referenced 4-mile road project. Now I fly all corridor projects this way.
Please let us know what you determine to be your best workflow. This is how we all learn, from each other.
Ryan Fontaine, P.E.