Help with survey grid over huge slopes

Take the case of wanting to generate a grid to map a land with huge orographic slopes (for example from 0 to 100). Let's also say you want to plan a mission where the drone flies at a constant altitude of 40 meters above the level of the ground below. As the distance of the drone from the ground remains constant, also the FOV on the ground remains constant, also overlaps remains constant...

Well.

If I try to plan a similar mission with Mission Planner, as in the Survey Grid mask I can set an absolute altitude, the footprint is reduced as the drone flies on the higher parts of the ground... so the software calculates a wrong flight path with wrongs footprints...

Please I need help...

The issue names Mission Planner's Survey Grid mask and its absolute-altitude setting, but no files, tests, or entry points. Start by reproducing a survey over slopes from 0 to 100 and compare the planned footprint at 40 meters above ground; done means the flight path maintains the intended ground distance and constant overlap.

Written by the indexing model from the issue text.