Last week, you learned about the spatial humanities, explored some map-based DH projects, and gotten an introduction to web mapping tools. Today, we are going to put what we’ve learned into practice and do some work on a class project using local Northfield history, as an example of the type of thing you might want to do for your final project.
To do this we are going to begin constructing a map of Northfield’s historic downtown. This process will involve several steps
- Georeference an historic map
- I have already done this following the process you used Monday, on a historic plat map of Northfield from 1900, courtesy of the Borchert Map Library at the University of Minnesota.
- Digitize features from the map
- We will trace building footprints and landmarks from the old map and add attributes to them to create a new vector GIS layer that contains historical information on downtown Northfield.
- Add contextual layers to a historic GIS
- We will leverage different sources and do some original research to figure out which buildings were present in 1876 and find historic imagery of them
- Make them 3D
- Next week, we will use the assets we have gathered to model our buildings in 3D using a few different methods.
Exercise (Digitizing)
Rasters are great for imagery or elevation values, but for most purposes we need GIS data in a vector format. Digitizing historic map data is essentially tracing features once you have georectified your image in order to create vector geometry. There are many ways to do this. One of the most accessible, is to use Google Earth, since it is free, widely available and often people’s first introduction to using a GIS.
Google Earth Example
- Google Earth will import rectified imagery in KML, Geotiff, and other file formats. If you export an image from your referencing tool, you can bring it into Google Earth by choosing File > Open from the menu and navigating to your file.
- As an example, you can use this map I rectified of Stillwater, MN
- A properly georectified map should be shown aligned over the modern satellite imagery.
- Now you can use the Add Placemark, Add Polygon, and Add Path tools in the top menu to digitize point, polygon and line features, respectively, from your georeferenced map!
- For instance you could pinpoint the old courthouse (a placemark, or point), trace the old shoreline (a path, or line feature), or trace the outline of a neighborhood (a polygon).
- As you create features you can add metadata, change the symbols, and change the location of the camera to save alongside the feature in the Get Info window.
- Finally you can right click your newly created features and save them as KML or KMZ files (a zipped version of KML) for use in other programs.
Collaborative Digitizing with GeoEditor
You’ve seen how we can use web mapping platforms like ArcGIS.com to add features as well. Online platforms, like most DH initiatives, have the added benefit of easy collaboration and crowdsourcing of labor to make detailed, time-intensive tasks more manageable.
For this project, we are going to try out the relatively recent GeoEditor tool by Klokan Technologies, the same people who make the Georeferencer tool you already used. They are developing an integrated suite of open-source software for the cultural heritage sector that allow old maps to be discovered, rectified, digitized and transcribed. While there are more precise GIS tools out there, the easy collaboration and integration with Google drive should make this one well suited to our group project.
To digitize using the GeoEditor,
- Log into your Georeferencer account, find the map you referenced (or any other map) and click theOpen in GeoEditor button
- Digitizing features is as simple as
- Picking the feature type you want to create from the point, line, or polygon icons at lower right
- Drawing on the map by clicking with the mouse
- Adding attributes with the Large Plus in the right-hand “properties” window and filling in their values
- And that’s it! Try it for a few minutes with your own map. When you are satisfied with your features, you can either
- Download a GeoJSON file directly to your computer, which you can then import into other GIS software
- Or Save the file to Google Drive. This option is preferable for collaborative workflows, since it leverages Google’s native file sharing capabilities.
Digitizing Historic Downtown Northfield
To digitize the features from downtown Northfield, we are all going to work collaboratively (fingers crossed) on a GeoEditor file of the 1900 Plat Map of Northfield, accessible at the link below.
1900 Plat Map of Northfield (GeoEditor)
You should all be able to edit this file, if logged in, since it is stored in our shared Google Drive folder.
We will begin to trace the features together, breaking up the map and assigning blocks to each individual so we are not stepping on each other’s toes. Once you have drawn the features for your block, fill in the attribute values as appropriate. Some of these may be apparent from the map itself, but for others we will need to do additional research.
- There are several sources of information you can draw on to populate this map.
- The Gould Guide on Northfield Area Data is a good place to start for various aspects of town history.
- You might also find useful information through the Minnesota State Historical Decennial Dataresource, although this tends to trend more modern.
- The most important source for our project will be the National Register of Historic Places database.
- This is a fantastic public resource that was an early form of crowdsourcing, relying on local communities to nominate places for inclusion in the registry. The Park Service has created a database of these places, complete with spatial information, and links to the original nomination forms and historic images that offer a wealth of information. You can search the database directly through the links on the page above or…
- I have combined the publicly available spatial data with the digitized plat map and some modern and historic county level demographic data from the NHGIS at the ArcGIS online map of Northfield Minnesota in Context 1870-1900, embedded below.
Click on the polygon feature and follow the links to the historic imagery and nomination form for the Northfield Historic District and other buildings in the NRHP.
- You may need to compare modern imagery (from Google Street View for example) with the street level images from 1978 or other earlier photos, to fill in the Floors and Material fields.
Assignment (Building Specifics)
The map we have digitized depicts Northfield as it was in 1900, but we want to get back to how the town looked on the day of the failed bank raid: September 7, 1876. To do this, we will gather more detail on the specific buildings that stood at that time.
- Find a building in the historic district that was built before 1876 and claim it as your own by filling in all the fields on our building data sign up sheet: Northfield Buildings Before 1876
- Now start search the archives and the internet for additional details and especially historic imagery of your building. As you find images,
- Collect them in Google Drive in your named folder, and add their metadata to our Building Research Data Sheet.
Next week we will use these data to build a 3D representation of historic downtown Northfield.
