Dead Confederates, A Civil War Era Blog

Only Cartophiles Need Apply

Posted in Technology by Andy Hall on August 18, 2011

One of the traits often ascribed to Robert E. Lee was his uncanny ability to read terrain. He had, according to some, an almost preternatural ability to see on the other side of the hill, to know intuitively how best to position his forces for maximum effect on ground he’d never traversed before. His engineer’s eye for terrain didn’t always serve him well, but it did more reliably than most officers’.

I thought about that when I discovered this index of (mostly) Civil War era maps from the U.S. War Department, Office of the Chief of Engineers records at the National Archives. It’s a very large collection, and most files can be either previewed in small scale (“access image”) size or downloaded, in TIFF format, at full resolution. To make use of the latter, you’ll need some good graphics software and a fast Internet connection; this chart, which seems to be the basis for the plan of Galveston in the OR Atlas, is a whopping 106MB at full resolution.

There’s also an index to plans of (mostly) Civil War era fortifications and military installations from the same records group. This set, interestingly, includes a detailed diagram of the tunneling done for the famous mine during the siege of Petersburg:

On a somewhat related note, I’ve begun working with ArcGIS Explorer, a freeware version of the professional ArcGIS mapping software. I never bothered much with ArcGIS because the desktop version simply wasn’t within my budget, but ArcGIS Explorer is free, with either online (Mac and PC) or desktop (PC only) versions. Furthermore, the full version, with all the bells and whistles, is now available for home use at an annual subscription rate of $100 per year, which puts it well within the range of all sorts of folks who had been priced out of the market before.

Folks who’ve followed this blog know how useful I’ve found Google Earth to be, particularly when it comes to overlaying historic maps and diagrams on their modern locations. It’s a bit of a headache to do, though, requiring lots of trial-and-error to scale, rotate and place the map overlay correctly. ArcGIS makes that process quite a bit simpler, provided you’re working with an historic map that shows precise points that can be identified on a modern map or aerial image. (It’s also essential that the historic map be an actual, surveyed map; there’s no point in trying to overlay a quick sketch map over a modern chart and expect things to line up.) ArcGIS Explorer allows only the minimum of three points to allign and scale an overlay, but (as I understand) the full version allows the user to plot additional reference points, which should make the alignment that much more precise.

But enough blathering on. If anyone out there knows of any ArcGIS tips or tricks, pass ’em along. In the meantime, here’s some cartographic eye candy, comparing an 1863 U.S. Coastal Survey chart of Charleston Harbor with modern, aerial images. First, Charleston itself:

Next, Forts Sumter and Moultrie:

And finally, the northern part of Morris Island, site of Fort Wagner, which has sadly been lost to erosion:

I still like Google Earth’s user interface a lot better. What’s the likelihood of the nice folks at Google implementing a feature allowing users to scale and align overlays by reference points?
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Image, top: Oblique view of Harper’s Ferry from above Loudon Heights, merging an October 1862 map by surveyor William Luce with modern aerial imagery. Generated with ArcGIS and blended in Photoshop.

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2 Responses

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  1. Karen Capria said, on August 18, 2011 at 3:34 pm

    Andy,
    Read your post with great interest. You mentioned having made some maps. You can share them at arcgis.com. Also, there is a group, American Revolutionary War Historical GIS Maps, on arcgis.com should you be interested in connecting with other folks with similar interests. Also the North American Cartographic Information Society has an upcoming meeting, http://www.nacis.org/. Best wishes for your continued efforts in historical GIS.
    Karen C.

  2. Lyle Smith said, on August 18, 2011 at 5:08 pm

    Beautiful work. Love maps. Google’s terrain map feature is a favorite of mine. If only they had that back in the day. A whole bunch of battles may never have been fought.


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