Using QGIS to Bring Historic Maps to the Present
The use of maps as tool for understanding the past is not a new idea. Maps have been an important resource for historians and others to examine the cultural and natural changes in the landscape. Maps by themselves, however, tend to be one-dimensional. They are removed from the place which they had once represented. There are new ways to enhance maps, however, with some computer magic.
Using GIS software like QGIS, one can take a regular google map-like website and overlay it with historic maps. This can allow the user to see how historic maps line up with modern ones. I used QGIS in this way to work on my project of historic maps of Lubbock County in Texas. Though instead of doing one historic map, I used multiple ones to show different decades in Lubbock County.
To start with, I used Texas Natural Resources Information System and went to the DataHub tab to find for historic maps of Lubbock County. By searching for “Lubbock” and filtering for only historic imagines, I was able to see all the maps they had of Lubbock that are historic. Most are from TXDOT and USDA, with the oldest set going back to 1940. Of course, different areas will have different results in time span, geography, and quality.
One of the map layers I decided to use was the 1970 map of Lubbock county. I created a folder on my computer for all of these files so that they would be easier to find. From there, I went into QGIS to set up my project. Using the XYZ Tile, I was able to add a live Google streets map needed for georeferencing the maps.
Before adding the maps to QGIS, I edited them a bit, mainly cropping out the unnecessary borders of the TIFF file. In QGIS, I went to the Raster tab and clicked on Georeferencer. This pulled up another window to add the maps. Clicking on the button that is a blue checkered square with a green plus sign, I added my first map. From there you click on the same point (or as close as you can get) on the background Google Map that you do on the historic one. It was a bit tricky at some points, but it did help switching between satellite and the default versions to pick out the same points in roads, terrain, or even county lines. For this, I did at least three points before clicking the green play button that adds the map to the project. It was important to check and make sure both use the same GPS system prior to adding the map. There were times where something was off and my map ended up in the Pacific Ocean. Once I was satisfied with my map, I added the other parts of the images.
Once all the maps were to my liking, I merged them into one layer to make for easier use. This was done by going to the Raster tab, Miscellaneous, then merge. From there I clicked on the four maps I wanted to merge and created one image. Then I removed the separate map layers for a cleaner project. With that layer done, I repeated the process again until I got all the layers that I wanted.
The goal of this project was to create a virtual map of the Lubbock County with different decades represented. This showed the growth and changes in not just the cites and roads, but the terrain as well. This project, while it did have some hiccups, was not too difficult, though is a bit time consuming. I hope that this blog helps anyone interest or working on a QGIS project.
