Here’s another treasure trove of data that’s ready and waiting to be added to your ArcMap session.
Over the last several years the New York Public Library has scanned more than 10,000 public domain historic maps and atlases of New York City and made digital copies of those maps available via its website. Recently NYPL took this project to the next level by creating a web tool that can be used (by NYPL staff as well as volunteers from the general public) to georeference the maps – i.e. pin the historic maps down to their location on a modern-day reference map. Click here to check out their blog post about the project. Or click here to check out the do-it-yourself MapWarper tool and/or browse through the thousands of maps that have already been georectified.
What’s the big deal about being able to look at historic maps in GIS? Here’s an excerpt from the NYPL blog post on the project that does a great job of explaining how GIS can shed new light on old maps.
So, what does this all mean? If we have documents related to past times and past places (old maps), then we can create data to “rebuild” those past times and past places. And if we “rebuild” old places in virtual space, we can then organize a universe of other information around those old places. Wouldn’t it be great to haveyelp.com and menupages.com, but for old restaurants and with old menus and prices? Or to have at least a smattering of old photos in a historical street view? Or to search the National Newspaper Digitization Project using a map interface? At the core of all of these dream-like research futures is geographic information, in machine-readable format. And to get there, we need to warp, crop, mosaic, and trace our old maps. That’s why we’re doing what we’re doing. And as a positive byproduct, the maps just so happen to become more useful at each step along the way.
Using the NYPL website to find GIS-ready historic maps is incredibly easy. I used the ‘search by map’ option to zoom into Prospect Park in Brooklyn to find georectified historic maps that I could download and add straight to my ArcMap session. A whopping 394 maps were returned in the results – i.e. 394 maps that I could download as a KMZ file and add directly to ArcMap to explore how this small chunk of turf grew, changed and evolved through time to become the place that it is now.
If you find maps in the NYPL collection that have the historic places or events that you are interested in, but are not yet GIS-ready, you can use the MapWarper tool to georeference them yourself. Here’s a link to instructions for using the MapWarper – along with a YouTube video that describes the process.