0.57 x 0.57 miles is a good estimate. The lot is more or less square.
Yes. Maintaining 15mph is tough because of elevation changes. The land has a 1,200 foot tall ridge in it, so the drone must gain (and lose) 1,200 feet across that 0.57mi span. Which is steeper than the drone can do while maintaining a forward speed of 15 mph.
Additionally, SFM algorithms struggle with repetitive environments like pine forests, where there are not clear points or lines they can align. GPS data helps somewhat, but if the pictures are too sparse then it can get confused and start stitching images together incorrectly. Additionally, too few images lowers the fidelity of the output and causes strange gaps and black spots in clearings (where the clearing is visible in one pass but obscured in another.)
Finally, radio transmissions require two flights due to that ridge. I need to fly once on either side or I lose signal. There is no accessible point on the property I can maintain visual line of sight across the entire span, and "mountain" is a pretty good radio signal attenuator.
I'd LOVE to have some automation help in developing a flight plan, as right now it's manual, and I'm creating little segments myself, individually placing points and grids. Several tools claim to support automatic elevation, but none of them do so well when you have a 1000+ foot cliff or a narrow stream bed that has cut 20 feet into the earth in your environment.