This afternoon, as I finished up Visual Explanations, and furthermore tonight, when I returned home from giving a talk and saw Megan’s insightful comment about ability to compare maps, I realized I had made a mistake of parallelism in my previous blog post. When I displayed the 1846 and Boschke maps of Washington, I didn’t display them next to each other, and more importantly, I didn’t display them consistently.
The Boschke map was rotated as drawn, because it was taking in the area of the original diamond-shaped, off-angle District of Columbia–thus was not drawn with north facing up. The 1846 map took in just the city of Washington, and was drawn with north facing up.
So to make them more comparable, I went back to our now old friend Photoshop. I didn’t, for now, bother with making them a consistent color or cleaning any damage (since it’s 12:31 a.m.–so if anyone sees me bleary-eyed in class, you know why!). But I did rotate the Boschke map, and crop it so that it was consistent with the 1846 map. Then, I put the two maps into one image, separated by a small white line. So, here is my work–I saved it at 800 pixels wide, so you can get more of a comparison by clicking on the image. Now it’s easier to see how the 1846 map just shows the city’s blocks, giving an illusion of a built-out city, while the Boschke map shows the city as it actually existed in the late 1850s–having grown significantly even since 1846.