Unfortunately I'm not allowed to limit the users to flat-earth-accurate zooms.

A colleague pointed out the projection formula http://mathworld.wolfram.com/MillerC...rojection.html - it maps the 'x' coordinate by subtracting it from a reference longitude, and calculates the 'y' coordinate by a sort of hyperbola transfer function, which gives an output of +/- ~2.303 for a range of input latitudes of +/- 90 degrees.

Can anyone assist me in getting from these formulas to a screen position?

Thanks,

Dave