How to use DimAngle in perspective mode?

I am attempting to dimension an unusual window’s ledge angle, that in perspective mode is reading 28.3°. Yet when I DimAngle it from side view it is coming out as 32.5°. I am being told that the angle is being projected onto the viewport hence why the angle is widening. In all honesty, I do not see why you would ever want the angle to be projected and widen - this would give you an inaccurate measurement. How do I therefore dimension this angle correctly as a vertical angle in perspective mode - when I attempt it, the command automatically executes DimAngle along the horizontal plane.

Thank you

The only method I can seem to use that works, is to create a surface parallel to each line and then DimCreaseAngle these two surfaces - this gives the correct 28.3° but surely there is a quicker method for dimensioning than this?

Hi James - dimensions follow the current CPlane, so you can set a custom CPlane in that view - you might be interested in looking at the OneView command.