Say I'm looking at a portion of a map that's displayed using Mercator projection with the view bounded at 40°N and 20°N. How do I compute the latitude of the point that's in the centre of that view?
I figured it's not 30° and can compute it by firstly projecting the bounding latitudes onto a square using Mercator, computing the middle point, and then projecting back onto a sphere. But is there a simpler way of achieving the same without having to project to and from Mercator?