jdtw

Just FYI, the filename extension can be omitted. E.g. http://lowercase.billyjanitsch.com/one

The Greenwich reference is just to let you know that you're dealing with a latitude and longitude.

~500ms with optimized Common Lisp: http://stackoverflow.com/a/18065714/2423072

That's an old(ish) version. They've probably done a bit of optimization. For example, with the (speed 3) optimization, and letting the compiler know that sum is a fixnum, I can get it down to <2 billion cycles: See my answer here: http://stackoverflow.com/a/18065714/2423072