|Don't ask to ask, just ask|
Given that the area between the +-70° latitudes covers 95% of the Earth's surface and 99.8% of the world's population; and the 0.2% inaccuracy represents a 0.00016 mm on a standard large scale (1::25,000) map -- or, you'd need a map 800 meters wide in order to be able to detect the inaccuracy between the actual and calculated position of a point -- the "general case" is not required for the vast majority of cases.
Hence why I passed along the information that the general case is not usually required, without in any way impugning the accuracy of your post.
I was simply pointing out that unless you run an airline -- and one hopes they know what they are doing -- the simple 2D trig approach to mapping GPS coordinates to map coordinates is usually good enough.
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
In reply to Re^8: Perl and Solving Trig/Converting GPS to x,y Cords