From 11 to 14 May 2018 we had a DTU skills training on Geographical Information Systems (GIS) Analysis, Mapping and Cartography with dr. Catherine Jones. We were trained on how to attach a historical to a modern map and how to add labels to the map. Afterwards, I practiced my new skills by attaching an historical map of Leuven (Belgium) from 1649 to a map of Belgium and labeled the old monuments mentioned in the original legend.
During the course we learned how to work with QGIS uploading existing maps and exploring the Bombsight maps of London. We also started from scratch ‘stitching’ an old map to the open street map or google maps based on points that we could still recognise and that overlapped. Depending on how recent and/or accurate the historic map was, we had to choose a different transformation type. Unfortunately, the interface of QGIS wasn’t entirely intuitive and it took some time to find the main features. Also, many of the concepts were new, but I eventually got the hang of it.
Later I decided to repeat the process with an historic map from Leuven, a city quite familiar to me. Since the resolution of an earlier map I tried to use during the tutorial was too low, I found a more recent map (from 1649, rather than 1541) from the Atlas van Loon. Before uploading the historic map, I set the projection to TRS89 / Belgian Lambert 2008.1 Although Leuven has changed a lot over the last four centuries, I could stitch the map mostly based on the locations of churches still in existence today. Once the eleven points were identified on the open street map, I used the Thin Plate Spline-function, which was suggested by the instructor as the best method to overlap historical and modern maps. The Thin Plate Spline stretches the historic map as if it were made of rubber to find most similarities.
Next we learned how to replicate the London Bombsight maps that were introduced at the beginning of the workshop. We inserted and adapted data points such as locations of bombs that fell on a certain day of the week, or flight paths and areas affected by larger bombs in London. For the assignment I located the original items of the legend in the historical map of Leuven and used the number of the location in the original legend as an identifier, and the name of the item in a second field of the data table. At first, I tried to find the buildings and locations (mostly churches, colleges and squares) in the order of the original legend, but after a serious struggle to find one specific item on the list, I decided to systematically look at areas of the maps and locate the numbers of the legend first before adding a data point. Once I located most of the points, I looked at the data table once more and realised I had made at least two mistakes by identifying the same building twice on different locations. Luckily the points on the map light up when you select a row in the data table. This made it easier to correct the errors. In the end I made a list of all the missing legend items and found a list with links to the heritage inventory that were useful to eventually locate them. I managed to find two more buildings, but 11 out of 74 were untraceable (even though for some of them I was certain about their location).
As for my experiment with the map from Leuven in 1649, other possibilities in QGIS are to add more labels and metadata to the item dots. Different colours for each type of building can be used, e.g. a university or a religious building. Another option is to outline the original city walls (the ‘binnenring’ and ‘buitenring’) or to identify which areas contained housing, where the gardens were, and which plots were used as agricultural areas. Although the QGIS interface is not easy to grasp, it is very useful for spatial historical research once you understand how to use the program. In conclusion, GIS analysis offers a deeper insight into the spatial dimension of historical research and extends beyond the value of traditional historical maps.
- The projection of a map is defined as a systematic transformation of the latitudes and longitudes of locations from the surface of a sphere or an ellipsoid into locations on a plane surface. See wikipedia.