The Footprint radius: kilometres along the ground from the point beneath
a Satellite to the horizon seen from its altitude, on a spherical Earth.
Given an elevation, the reach narrows to where the Satellite stands at
least that high above the horizon: ten degrees is where it clears the
buildings, the hills and the haze a real horizon has, the reach within
which someone looking up can actually see it.
The Footprint radius: kilometres along the ground from the point beneath a Satellite to the horizon seen from its altitude, on a spherical Earth. Given an elevation, the reach narrows to where the Satellite stands at least that high above the horizon: ten degrees is where it clears the buildings, the hills and the haze a real horizon has, the reach within which someone looking up can actually see it.