QGIS has georeferencing capabilities that allows an image of a historical map to become a raster layer by assigning points on the map geographic coordinates. This post experiments with said capabilities based on the tutorial from the Programming Historian. That tutorial was based on an earlier version of QGIS, and so there were additional experiments in trying to do the lesson with the current version of the program. 

The first item in the instructions was to install the GDAL Georeferencing plugin, but after some searching realized this was no longer a separate plugin, but a standard built in tool. The use of the tool was also a little different than described. 

The actual first steps involved setting up a new project, defining the CRS, and adding two vector layers, one being the coastline vector and the other displaying the lots of Prince Edward Island. From this point, I selected the Georeferencer found under the Raster menu.

This opened a separate window and a dialogue box. Again, the CRS had to be defined and the image of the historical map added.

Next was the adding of points and getting them to correspond to points on the map just started with the coastline and lot boundaries. Selecting the add point tool, you click on an easily definable spot on the historical map, along the coastline worked best. Once clicking such a spot, a dialogue box opened, and the key here is to select the option in the bottom left corner to enter coordinates from map canvas. Selecting this takes you to the main map so you can click the same spot on the map, giving the geographic position of the one map to the other. 

This process was then repeated several times, adding sufficient data for the computer to be able to chart the rest of the historical map based on these given points. 

coordinates set and ready to georeference

Then the georeferencing settings had to be set so the new raster could be named and given a file location, again do this by clicking the ellipsis instead of simply entering a name in the output raster field. Selecting “load in QGIS when done” automatically adds this raster layer to the map in the main window.

Finally, click the triangle play button to run the georeferencing and watch the progress bar progress.

After that, the new raster is added to the map, and as seen, the historical map raster lines up very closely with the coastline and lot vectors already there.

final map, with new raster and vector layers correctly aligned.

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