April 4, 2014
How the New York Public Library is bringing old maps to the present
by Claire Kelley
The New York Public Library’s Map Division has published more than 20,000 historical maps online, which are available for browsing and downloading in high resolution. It has now also launched an interesting new digital tool to “rectify” these historical maps, and the library is encouraging anyone who is interested to help and participate in the process. Library patrons and website visitors can use the tool to bring older maps to the present by using anchor points to stretch and superimpose them onto to modern day digital maps. A blog post by Matt Knutzen, who is leading the project, explains:
The next [enhancement] is georectification, which we are calling here “warping”, a familiar term to GIS professionals and few others. Map “warping” is the process where digital images of maps are stretched, placing the maps themselves into their geographic context, rendered either on the website or with tools such as Google Earth.
Getting involved is easy. After signing up for an online account, you can find old maps by searching for a city or neighborhood. I searched for “Navy Yard” and found this map of Brooklyn.
Next, you use a tool to match anchor points from the historical map to a modern day map, which takes into account the curve of the earth, information included on modern digital precise maps. This particular map had already been “rectified” so I could download an updated, stretched, and more accurate map.
Finally, there are tools to see how the map looks on top of Google Maps, to get a sense of what has changed. In this map, you can see that the historical map pre-dated Pratt Institute.
Others have explored the process of rectifying maps in order to learn more about Chicago, lower Manhattan, and the New York transit system. Libraries like the Los Angeles Public Library and the Boston Public Library have excellent map collections that are fun to explore too.
Here’s a video from the New York Public Library that explains more about their map initiative and how to participate.
Claire Kelley is a the former Director of Library and Academic Marketing.