Calculating FOV / Overlap for Roof GSD (RSD) ?

If you have a roof that is 40 feet off the ground, and you want a GSD that requires an AGL altitude of 20 feet, then you have to fly 60 feet off the ground.

However, the effective overlap and sidelap will not be the same for the roof which is 40 feet closer to the camera as the closer the object the faster it moves through the frame.

How do you calculate what you need to increase the overlap and sidelap to, to get an effective overlap of objects in a plane of the photo that has a smaller field of view than the ground?

is there an “RSD” mode you can activate?


No software can account for every situation so the mission planner and/or pilot has to do manual calculations.  Some times it is as simple as using the Pix4D GSD spreadsheet or setting the software for a 20 foot height and copying the look in the 60 foot height by increasing overlap.

Personally I never believe the calcs in any flight app and do my own estimating to make sure I don’t have to re-fly the site.

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