How to calculate the height of installation for a CCTV camera?

IF you want a fairly accurate estimate of the height of an installed
CCTV camera (say, on a street or in a square), note your eye level on
its mast or building and then back off.  Using a 45° angle (diagonally
folded piece of paper) find a place where you can sight to the
imaginary spot at the base and to the camera.  Measure that distance
and add your height to eye level.
People may look at you, maybe the camera, too.