For this week’s blog assignment, we created a georectified map of the current layout of Northfield with the original city plans.
Creation:
In class, we made the overlaid maps by cross-referencing control points on both the original and the current layout. Some key places that were easy to pick out included Central Park, Willis Hall, and some St. Olaf locations. Then, we used Allmaps to create an overlaid image, and the software allows you to adjust the strength of the background to view both at the same time. If we had more time, I would adjust the corners of each block to be lined up perfectly, because the map did become warped a little bit (as you’ll see in the viewer I linked below). Other than some offset lines here and there, I thought our map was pretty accurate.
Here is our map on the Allmaps viewer and XYZ map tiles.
Reflection
I think this process made me realize how much time was put into creating accurate maps for some of the projects we explored earlier. It was already tedious to set just twelve control points, so I can’t imagine how long it would take to accurately georectify a map of all of the counties within the United States. I could see a lot of potential benefits of this process in environmental science. Having a georectified map would be really helpful to compare things like coastline changes, deforestation, or erosion over time. On the flip side, some problems I could imagine might occur include distortion errors or scale issues if the area has changed drastically or if the maps are on different coordinate planes. Also, the information that the georectified map can provide is very limited to the information that the original map included. It would be impossible to discern topology changes if the original map was not a topology map.
Conclusion
When done accurately and with a specific area of interest in mind, georectification can be extremely useful!
