Mappacks that take a "latlon center" instead of corners

[mentat]

A lot of the public map servers serve out maps give a latlon center. It would be a lot easier to import these into JiGLE if mappacks could be defined by a center, but then there is the scale and image resolution to take into account. Does anybody have any good ideas on how to do it? I need to take a closer look at the gpsmap code.

[uhtu]

do you have any scale information/example site/urls?
may be able to accurately derive corners from center given enough information.

[mentat]

I was thinking about stuff like mapblast and mapquest where you request the center at a certain resolution and scale and can then derive the corners. I know there's something like this in gpsmap and fetchmap (or whatever the gpsdrive map fetcher is) but I didn't understand how they work.