I'm using a new technique to make the maps, snapshots of Google maps areas, cleaned up and stitched together using GIMP. I'm not a GIMP expert by any means, but I've been able to figure out how to do things with it fairly easily. I'm running a campaign set in a fantasy Roman Republic, just after the fall of Carthage and about 90 years before Gaius Julius Caesar invades Gaul. So Google Maps can be used to build my campaign world. Of course, any large scale (small area) fantasy setting could be mapped over piece of the real world terrain using these techniques.
I saved the image off onto my laptop and opened it in GIMP.
The cross hairs on the pointer (not shown) identify a point on the image, by hovering over the top of the lower control bar, the pointer location circled in the bottom corner of the screen shows that it's at pixel 752. Similarly I used the pointer to find the bottom of the top control bar, at pixel 58. 752 -58 gives us an image height of 694.
Using Image -> Canvas Size from the menu I reach this dialog
Click on the chain icon (1) to decouple the image Width and Height, as we don't need to trim the ends. Set the desired image height (2). Set your offset from the top of the image (3) - not sure why the value '58' didn't get captured here. Select to resize All Layers (4), click Center (5) and then Resize (6). And you have successfully trimmed your image.
In my next post I'll cover techniques for getting rid of those pesky labels, modern roads and borders from the image.