I have been long curious about the exciting functionality of using historic maps for layering various types of information in digital humanities projects. However, I’d been putting off actually doing it until now, when several of my students in Introduction to Digital Humanities (see the syllabus here) chose to do it for their final project. In trying to figure out how to help them with their project, I remembered why I’d avoided it for so long – I couldn’t find any tutorials that didn’t involve complicated server knowledge.
What follows is a tutorial for using Neatline with historical maps that does not involve downloading software (if you already have a Neatline.org instance installed). It covers how to load a georectified map into Neatline, as well as how to georectify a map yourself. You may use an already rectified map, or you may use a scanned image of a map that still needs to be georectified.
Included below are steps to:
- Use an already georectified map (from NYPL Map Warper)
- Georectify your own map
- Load a georectified map into Neatline
[Dec. 2016 update: This tutorial is now the first in a series of three on using georectified maps. Find out how to put a georectified map into Mapbox and Tableau here. Find out how to put a georectified map into Carto and Esri Story Maps here.]
This tutorial assumes that you have an Omeka.org installation set up with the Neatline plugin installed.
Use an already georectified map:
- Go to NYPL Map Warper at (maps.nypl.org/warper)
- Search among “rectified maps only”. Among your search results, or from browsing on the home page, select a map by clicking on its title.
- To download the map, click “Export”.
- You don’t need to download anything to use for Neatline, however. You just need to construct the WMS url for your map. The standard URL for NYPL Map Warper is: http://maps.nypl.org/warper/maps/wms/[YOURMAPNUMBER]. To discover your map number, look to the URL in the NYPL Map Warper. You should see maps.nypl.org/warper/maps/[NUMBER]. You can also find the number by looking above the map title to Home>Search>Maps>Map [NUMBER].
- In my example the WMS URL is http://maps.nypl.org/warper/maps/wms/26900. Also note the full title of the map. In this example, it’s “Official transportation map Michigan”. Save these for later.
- Skip to “Load a georectified map into Neatline” below.
Georectify your own map:
- Make sure to have an image file (ideally TIFF) of the historic map.
- Create an account with Map Warper (mapwarper.net)
- Click “Upload map!” at the top
- Enter a Title, description, tags, and other metadata. The more thorough you can be, the better. Upload the image file, and click “create”.
- You will be taken to the editing page of your map. The “Edit” tab allows you to change, add, delete the metadata fields you just entered.
- The “Rectify” tab is where you select points on a gps map and on your map image.
Create at least 3 control points, but the more the better. Once you have enough control points that you feel comfortable, click “Warp map” at the bottom of the screen.
- The “Crop” tab shows you a map of the world. Zoom in to where you’d like the map to center, click on the polygon in the top right of the screen, and draw lines around the map to crop it, double clicking when you have completed the shape. Then click “Mask Map!” at the bottom of the page.
- See what the rectified map looks like by clicking on the “Preview” tab
- To download the map, click “Export”. You don’t need to download anything to use for Neatline, however. You just need to construct the WMS url for your map. The standard URL for Map Warper is: http://mapwarper.net/maps/wms/[YOURMAPNUMBER]. To discover your map number, look to the URL in mapwarper. You should see mapwarper.net/maps/[NUMBER]. You can also find the number by looking above the map title to Home>Search>Maps>Map [NUMBER].
So in this example, the WMS url is: http://mapwarper.net/maps/wms/11408
Load a georectified map into Neatline:
- Log into Omeka and click on “Neatline” in the left panel.
- Click “Create an Exhibit”
- Enter in the Title and other relevant fields.
Select the “Default Spatial Layer” that you would prefer to be the background of your historical map and its surroundings. Remember to check the “Public” box if you want your exhibit/map to be visible publicly. Save the exhibit.
- Select the title of the exhibit you just created – doing so will take you to the Exhibit Editor.
- Exhibit Editor looks like this. Click “New Record”
- Click “Style”
- Then scroll down…
Until you get to the “Imagery” section. Paste or type in the WMS URL you created earlier into the “WMS Address” field. Enter the title of your historical map exactly as it appears in Map Warper into the “WMS Layers” field.
Then, recenter and zoom the map however you prefer, click “Use Current Viewport as Default”, and “Save”.
- Now your georectified historical map displays onto the basemap and the basemap is zoomed and centered how you like. But the historical map is very light. Scroll up to the “Opacity” section and increase the values to your liking. I prefer to increase opacity to 0.8. Click “Save.”
Scroll to the top of the record editor and return to the exhibit editor main page.
- Make sure to rezoom and refocus your map if necessary. Click “Styles”, “Use Current Viewport as Default”, and “Save”. Now your historical map will be the default center of your exhibit.
Thanks to the Neatline team for their website and documentation materials (found here). Special thanks to Lincoln Mullen (@lincolnmullen) for his “How to use Neatline with Map Warper instead of Geoserver” blog post (found here).