Occasionally, I like to go through the QGIS plugins and see what’s new. There are all sorts of handy tools in there, but one in particular caught my eye this time. The Historical Map plugin, by Nicolas Karasiak & Antoine Lomellini, takes on a specific challenge: extracting data from old maps. Of course, you can always digitize this data, but it can be quite time consuming. The plugin leverages image classification techniques to speed up the process. The nice thing about historical maps (such as USGS topos) is that there are usually fairly discrete color codings. Discrete colors takes a lot of the guesswork out of the image classification process, but the techniques can be pretty intimidating if you haven’t done them before.