This week I georeferenced an old map of Northfield. Georeferencing is the process of aligning spatial data with geographical coordinates that helps us map our surroundings with precision. The form of georeferencing I did is called georectification. To begin the georectification process, I found this map in the Minnesota Digital Library. After that, I mapped out 14 coordinate points to overlay the image with accuracy. Then, after lowering the opacity and background, the result was a georectified map. It can be found here.
City of Northfield original plat, 1905-1910, Northfield, Minnesota
This process definitely gave me a greater understanding of GIS and spatial DH projects. Looking back on mapping projects I explored earlier, I can appreciate the effort that went into gathering historical maps and plotting all the points, lines, and polygons in an innovative and visually cohesive way. I only used 14 points, and I found out how just 1 inacurate point can distort the whole map.
Despite the specialization of the software, I found Allmaps to have some customizability. For instance, there were three background maps: ESRI World Topo, OpenStreet, and ESRI World Imagery (which was 3-dimensional). It is also possible to add custom layers. Additionally, Allmaps provides a lot of metadata to help better understand the context of the project.
Georectified maps are very useful in DH projects. They give you valuable spatial data that you can analyze and present in many ways. Common next steps include adding layers, building 3D models, and creating relevant labels for your project. It is widely used in fields like historical research, real estate, and satellite imagery.
While it’s useful, it is not without drawbacks. In this article, the author recounts their struggle to map rural and foreign locations, which have very little data to go off of.
If I had not conducted further research into Judge Peters, I may not have discovered what Belmont truly was.
“Challenges of Georeferencing,” The Historical Society of Pennsylvania
Because the data distribution isn’t equal, neither is the quality distribution. Open Google Earth, for example, and you will see well-defined maps in the cities and blurry images in Antarctica.
While georeferencing with AllMaps works well for experimentation, it isn’t a good tool for research. Though the product is digital, the data input process is still manual and subject to human error. However, georeferencing can be valuable in research with more complex software.
