If you're curious about coordinates of a map, you might be interested in using BSPViewer. You can float around and it will tell you your origin (the location of your viewport in the map).
While it is possible to write a plugin to teleport to the origin, it won't actually be that useful IMO, I would just use BSPViewer.
Regardless, I don't think you even need to do this because, as Natsheh said, the data you need is in the TXT file that comes with the overview of the map (you'll need to use that overview or one that is equivalent for the image you're planning on putting your player locations on).
If you look up on how to make overviews, it will probably have some good info for what you're trying to do (because you are literally doing exactly what the game does already in the minimap).