As suggested in the tutorials, a good flight-planning practice is to fly 2 routes, 20° off one another. My question comes from the following phrase:
“To get good 2D and 2.5D (digital elevation model) results, you will require 42% overlap and sidelap for an equivalent 70% overlap and sidelap.”
I use DroneLink for mission planning, which has a “Front Overlap” and “Side Overlap” option in the mission planner. I usually go 75% Front and 75% Side, but I was wondering if I could save myself some time by lowering the percentages X amount each, to whatever value(s) result in “an equivalent 70% overlap and sidelap”.
Are those front and sidelap values dependent on height, or is height arbitrary when only generating orthos?
How much you can dial back depends upon a number of things, including height, scenery, sensor and lens, speed, lighting.
What are you imaging? Things like dense tree stands do not really tolerate lower overlap and sidelap.
As already suggested - it depends! For mostly flat agricultural land with consistnt height cropping or trees (citris) after much trial and error I generally fly with 75% Front and between 60 and 65% side* I Adjust the side slightly to get the coverage required. But I am strictly looking at 2D here and not even processing 3d point coulds from these datasets.
the 3rd variable is of course how high I am flying. While this of course sets the absolute limit on resolution, Where high res is important i will fly lower with greater overlap.
Again, this works for me in this situation, so the best thing to do is to go out and try for yourself - go and plan a mission, Fly it multiple times, making a note of the variables each time and you will work out what is acceptable to you.
For more complext terrain or where I need 3D the sweet spot is 80-85% Forward and between 75 and 80% Side. Again this will be dependent on the camera as well.
There really is a no one size fits alll approach.
I am imaging residential and commercial lots strictly for orthophotos, no 2.5D or 3D, so it’s a little bit of everything: warehouses, parking lots, tree canopies, fields, roads, etc.
I only have 4 batteries with my Air 2s, so I’m only asking about the overlaps because changing the sidelap will lower the overall mission time on Dronelink.
I guess my original question should’ve been: where does the “42%” value come from, exactly?
Frontal overlap can (in some cases) compensate for sidelap, so always crank it as high as it can go on your platform. It just costs storage and (a bit more) processing time.
Sidelap is tough to tune. You may have to experiment a bit to optimize for your expected time in field.
I’m not certain of the math to derive the 42% figure. Stephen would have to elaborate.
I suspect that since 0.65 is the square root of 0.42, flying 2 passes offset to some degree at 42% overlap will give you effectively 65% overlap in total, sometimes considered to be the minimum useful overlap.
Or something like that
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