I missed class on the day that we worked on georectifying, and I also couldn’t dig up the link to the georectified map of France that I used for the second half of the week (I may keep looking and put it in tomorrow). I think I have a decent sense of the process involved, however, having read the materials discussing it this week and also having applied georectified maps as layers on web maps.
I guess there had always been a blank space in my understanding of how maps become digitized, interactive, and comparable, which georectifying has begun to fill. I’ve had a decent amount of interaction with historical maps in print — mostly medieval and early modern ones — and in a weird way, I think I hadn’t really been thinking of the trade routes, territorial lines, cities, etc. on those print maps as being places that correspond exactly to modern coordinates, modern places. Some of the boundary lines in maps from those periods have changed or are inaccurate to the shape of the continent, or in a different perspective, so that can make it surprisingly easy to forget what you’re dealing with. I’ve seen maps of parts of the Americas by indigenous mapmakers, for example, that use shifting perspective, aren’t to scale, and use their own visual language. Those differences are factors that could make georectifying both fascinating or potentially very confusing.
For the purpose of this blog post, I’ve ended up looking at this map of Great Britain and Ireland. I can view this map in overlay, grid, swipe, and spyglass modes, each of which allows me to see different portions of the base layer map against the historical map on top. I can also add other maps to compare it with in these modes. This is really exciting to me — I could compare one mapmaker’s maps of different regions in one view, or I could compare two mapmakers’ maps of the same region and see how their depictions differ from one another and from the stable base map.
