NYPL Map Warper

One of the New York Public Library’s many crowdsourcing projects is the Map Warper project. The purpose of the project is to align digitized historical maps with today’s highly precise maps. The library scans the maps, charts, and atlases from its extensive collections and then the public does the work of rectifying the historical maps. The result is the ability to overlay the historical and modern maps with a whole spectrum of transparency. This allows the viewer, researcher, or collaborator to experience changes in the geography as well as in the mapmaking process.

To join the project is quite simple; all that is needed is to sign up for an account. There is a quick three minute video that clearly explains the process with visuals of the website. There is an enormous range of maps to choose from. They are searchable by location and layers (the same location over time). When browsing all maps, the status column can be reorganized to show unrectified maps at the top.

I chose a 1603 map of the Diocese of Liege in Belgium. Once chosen, a split view of the historical map and the modern map shows up. I had to find three control points between the two – three places that were the same. I had some trouble at first as I didn’t realize the two maps were oriented in completely different directions. Once the control points are found, I cropped out the border, and the overlaid map was visible. The historical map was oriented around rivers and it was gratifying to see most of the rivers match up around the edge of the overlaid historical map.

I can see this database as quite useful for research questions about map-making, organization of space, and urbanization especially as it relates to New York City. Perhaps the biggest use for the rectified maps is their usefulness in creating map and space based visualizations.

The process of rectifying the maps was quite simple to learn and there was a range of maps in terms of difficulty to work with. Overall, the time needed was much less than I originally thought it would be. And the technical savvy needed was also minimal with clear explanations and a user-friendly interface for establishing the control points. I would definitely work with the group again. Additionally, seeing how perceptions and organization of space has changed is fascinating. The historical maps really do become warped in the process of fitting them to the modern map.


Student in the World History M.A. program with interests in the intersections of imperialism and gender in the Atlantic World.

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