I'd personally say the zoom has something to do with folding it: You can unfold it to look at the whole thing, or fold it down to show a particular place of interest, which makes that place appear an ideal size, even though it's not that size when folded.
The other thing I'd say is avoid letting your players use google Maps for this. Say the map is detailed differently then a traditional road map and you can have it only show the details you find relevent. After all, the inteligence from the map would likely navigate the world differently 200+ years ago: new roads have been paved, new landmarks, etc. This gives you oppertunities to add challenges that wouldn't be there otherwise.
E.g. "We're supposed to turn left at the 50' rock!" - "Wait, what? There's no rocks here!"