From: Cologne, Germany
Practice on a small map/project first.
If you can't obtain maps for your specific project, or if you're in doubt regarding the interpretation of topographical values/issues, obtain sat views.
Google earth can be helpful here (as cheap solution for first timers or for ppl who don't head for hist. accurate maps), as it provides you with a good overview to direct your project.
While streets, villages, cities, even rivers may have (been) changed in 60+ yrs, the topographical signatures remain the same, usually.
To practice, try and use google earth: http://www.matrixgames.com/forums/tm.asp?m=1173489
G-Earth provides a ruler, which isn't uber-accurate, but which helps to create underlays for the SM. G-earth also allows to use (adjustable) transparent layers.
In the example above you may barely spot parts of a different map displaying ferry routes in the right bottom corner. It also displays the current/only highway....plus, it showed me that recent route maps are extremely inaccurate, as towns tend to be drawn up to several miles away from the actual spots compared to today's available sat-views, that's why you should head for the maps mentioned in other posts, if it comes to hist. accuracy.
I'm not using g-earth to draw this isle's infrastructure, but to verify that mountains or valleys are drawn correctly, and to display differences between current and past layout of the infrastructure when verifying the few ancient maps at hand.
General Anthony McAuliffe
December 22nd, 1944
"I've always felt that the AA (Alied Assault engine) had the potential to be [....] big."
8th of August, 2006