Thought that most GPS software converted the image file into it's own format, I could not find one that would accept large, high resolution maps.
I copied the autoroute screen (Alt & PrintScreen) & pasted this into Paint, which I used to trim off the non map bits, using copy & paste, as Paint does not have a crop option.
Never managed to get the GPS software to load the image.
The Autoroute location sensor (Tools>Location Sensor) will enable you to display latitude & longitude for the corners.
At least some of the GPS software will automatically move from one map to the next, when it gets to the boundary, so negates some of the benifit in having large maps.
You also need to find some decent GPS software that will work reliably with a GPS unit, I found it to be very hit & miss, mostly miss
Mike