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Citizen Cartography Workshop


Help NYPL build the geospatial library of the future! This workshop will get you oriented with the a set of tools the Library has developed (available at that enables librarians and the general public to add valuable geographic context to old maps. The workshop will focus on the core activity of the website: georectification, or "warping" maps. This means overlaying digital images of historic maps onto a contemporary digital map (similar to Google Maps), transforming them into tiles of a virtual atlas.

The above image shows a warped map sheet from an 1857 William Perris Real Estate Atlas depicting a section of Manhattan to the southwest of Union Square (see it in the context of the Warper). By stitching this to its sibling sheets from the atlas, we can build a complete 1857 historical layer of Manhattan, observing changes in the street layout and conjuring the ghostly footprints of old buildings. This is just step 1 in a larger integration effort, in which we can pull together archival records, newspapers, photography and other literary and historical documents that are associated with places on the map.

There are literally thousands of maps to process — far too big a job for NYPL to do on its own. So we're enlisting you, our Citizen Cartographer corps, to help lay the foundations of a powerful new research tool that will benefit scholars, educators and history enthusiasts around New York and the world.

Once you learn to warp, you can do it anytime from the comfort of your home, and even teach others how to participate. If you can't make this workshop, keep an eye out for upcoming offerings, or simply watch the tutorial at and get started on your own!


More Info

  • Audience: Adults