Pastel lakes and gentle greens frame this map of Lake Istokpoga, Florida. Without any sort of legend, however, it’s hard to tell precisely what the rest of the features are supposed to be. This “experimental raster processed map” was produced by the Defense Mapping Agency as part of a U.S. Army program to test new techniques for automating cartography. To make the map, the cartographers printed eleven different hand-drafted manuscripts on semi-transparent mylar—each one consisting of a different geographic feature, like water bodies or railroad tracks—with the help of computer technology. This process of “layering” remains central to the production of digital maps today, although it all now happens inside the memory of a computer, rather than with physical transparencies.
The sheet attached to the back of Lake Istokpoga provides a detailed account of how the Defense Mapping Agency made this map. Computer processing was performed on each “class” of data—such as roads or water—to thin out lines, merge features, and convert information.
This production technique highlights an important distinction between cartography, which deals with all aspects of map design, and compilation, which refers to extracting geographic information from primary sources like aerial photographs and turning those observations into structured geospatial data. Both processes required lots of manual labor, and many people viewed computers as a way automate the work, saving both time and money. Lake Istokpoga is a product of this generation of maps that successfully pushed the boundaries of compilation; as one technical report from the Defense Mapping Agency notes, the aim was to produce a device that would “allow the production center to go directly from digital data to a pressplate”—a goal that was radical at the time but which we take for granted today.