I've got a series of longitude and latitude coordinates which represent a building outline
-0.5485381346101759,53.2285150736142 -0.5482220594232723,53.22842450827133 -0.5482298619861881,53.22841205254449
...(intermediate points not listed)...
How can I work out the midpoint? I've found tutorials that show how to do it if you've got three coordinates (e.g. http://mathforum.org/library/drmath/view/68373.html), but in many cases I've got more than three.