Esri's ArcGIS Online supports over 100 projections, and they're always working on more.
I had the privilege of chatting with one of the developers there who works on their projection engine (which is unmatched in the industry, as far as I know). To contribute to it, one effectively has to be at the graduate level in mathematics, low-level programming (especially numerical methods), and geography at the same time.
I had the privilege of chatting with one of the developers there who works on their projection engine (which is unmatched in the industry, as far as I know). To contribute to it, one effectively has to be at the graduate level in mathematics, low-level programming (especially numerical methods), and geography at the same time.