I'm new to using player/stage, and I'm trying to simulate a gps device on a robot.  I can't seem to find a single example of a stage .cfg and .world file where someone is using a robot with a gps device on it.  I am getting errors and I think the problem is in one of those files.
When I call requestInterfaceGPS(), I get the following error:

error: stage driver doesn't support interface type 13

What I'm trying to do should not be impossible because there would then be no reason for the existance of the GPS interface.  I think all I need is an example .cfg and .world file to work off of, one that simulates a gps device.  Where can I find one?