What about deviations from flat ground and vertical objects?

Very nice tool!

Just a reflexion as food for thought for a possible improvement:
If I understand well how the software works, I feel that people using it on uneven or inclined ground will end up with erroneous results due to the effect of the angle of the ground with respect to the horizontal on the observed shadow length.
More generally, if the whole picture is tilted, then we do not have any good reference frame to express the object true vertical height and the shadow length.

Should this be taken into account and if yes how? Would it be possible to measure and input an offset with respect to a right angle?

The issue does not name a file, test, or entry point. First trace how ShadowFinder currently models ground angle, object verticality, and shadow length, then determine whether an offset can be measured and entered. Done would require an agreed method for handling uneven or tilted scenes, with validation for the resulting measurements.

Written by the indexing model from the issue text.