Submitted by Sammy Smith (firstname.lastname@example.org)
You may not know about free software that lets you “fly” across the Earth’s surface, viewing satellite pictures of the surface below. The software for doing this is provided free by Google, and is called Google Earth.
As they say on their website:
Google Earth lets you fly anywhere on Earth to view satellite imagery, maps, terrain, 3D buildings, from galaxies in outer space to the canyons of the ocean. You can explore rich geographical content, save your toured places, and share with others.
Remember, you need a fairly fast broadband connection and video processor on your computer to do this.
One fun thing to do with Google Earth is to overlay old maps on the modern landscape. The example here is a historic map that I found in the Library of Congress online map collection. This map was created in 1864 by Robert Knox Sneden (who lived 1832–1918), and shows the Atlanta area as of 1 September 1864, complete with batteries, earthworks, and the locations of both Union and Confederate forces, as well as city streets. Remember that the city of Atlanta fell to Sherman’s army only a week later, on 8 September. The Virginia Historical Society holds the original map, which measures 45 x 34 centimeters.
In this article, I’m just examining a portion of the entire 1864 Sneden map, the part that spans downtown Atlanta. The top image shows the small cropped area of the old map on the right, with the same area from Google Earth (north is “up” in both cases). I’ve put arrows to the same features on both maps. They are a particular street and the location of the Civil-War-period train station. You can see the city plan is very similar, except for the interstate corridor east of downtown, and some alteration of the north-south rail line on the west side of downtown.
Below is a picture that shows how when you overlay the map image on Google Earth (or “drape” it), the software gives you bright green “handles” to stretch and manipulate the inserted image atop Google Earth’s satellite view.
Why don’t the maps match exactly? Do you know what the global positioning system is? How has map-making changed since 1864?
Here’s a link for the Sneden map.