Today we’re releasing Surveyor, a new tool to explore The New York Public Library’s collections of historical photographs, with one goal in mind: to make it easier to find NYPL’s digitized photos by the location where they were taken.

The collections of NYPL’s Wallach Division of Art, Prints and Photographs, Schomburg Photographs and Prints Division, Manuscripts and Archives Division, and Milstein Division together hold hundreds of thousands of photos, many of which show New York City’s ever-changing streets, buildings, and waterways. Browsing these photos allows anyone to travel back in time to take the elevated train down Third Avenue, see the makeshift huts housing Manhattan’s poorest residents, and compare the docks and warehouses of the city’s waterfront with how the city looks today (the buildings in that photo, actually, are still there!).

A large number of these photographs have been digitized and are available online in our Digital Collections. And our photo collections don’t just cover Manhattan, but hold photos taken in all the five boroughs and beyond—from Pelham Bay in the Bronx to Tottenville in Staten Island and Gilgo Beach on Long Island.

Finding photos of specific geographic locations, however, can be difficult. Although the title of the photo usually describes where the photo was taken, this is not always the case. The locations mentioned in photo titles often are very general, and only include the neighborhood or the name of the street. Moreover, modern maps and websites like Google Maps are useless when trying to find the locations of these photos when the addresses and streets in their titles have changed or no longer exist.

Still, this hasn’t stopped people from creating interactive maps to browse the Library’s photos. A famous example is OldNYC, made by Dan Vanderkam. OldNYC shows the locations of almost 40,000 digitized photos from two of NYPL’s photo collections. Using computer vision and optical character recognition (and a little help from NYPL librarians), Dan was able to extract location information written on the back of each digitized photograph. In turn, he used an automated search on Google Maps to find the street intersections mentioned in this text. Dan has written an excellent series of blog posts about this process on his website. In his last blog post on OldNYC, Dan explains how he overcomes the problem of finding streets that no longer exist with a modern geographic search engine like Google Maps.

OldNYC made use of locations written on the back of old photos, but the majority of New York City photos in NYPL’s Digital Collections have only vague titles or no location information at all. Algorithms and geographic search engines will not help us to map these photos, but crowdsourcing will. Over the past seven years, we’ve successfully used crowdsourcing to georectify our collection of maps, turn our collection of historical menus into searchable data, transcribe our oral history project, and extract historical addresses and building footprints from atlases of New York City. Now it’s time to use crowdsourcing to put New York City’s history on the map!

Today, we’re proud to release Surveyor, our new website for crowdsourced geotagging of NYPL’s photo collections. With Surveyor, we invite everyone who is interested in the history of New York City to try and determine the locations depicted in these mostly unlabelled photos. With your help, we will create a database containing the geographic locations of our photos, and this data will be available for everyone to use and download. We’ll start small, with around 2,500 photos from five collections, but we will add more of the Library’s photo collections later (you can find a list of these collections on Surveyor’s About page).

Of course using crowdsourcing to geotag historical photos is not a new idea at all. Websites like Historypin and Ajapaik, to name just two, have been doing this for years. However, we’re trying to take a slightly different approach. First of all, not only is Surveyor’s source code open source and available on GitHub, we will also release the crowdsourced locations of all our photos as open data—data that is freely available for anyone to use. Second of all, Surveyor will not just capture the point location of photos, but asks users to mark the direction and angle of the view of the image. This information will prove useful in determining whether photos exist of a certain building, especially in areas of the city that have changed a lot over time.

But the last and most important aspect of Surveyor is what the Library will do with the location data of our historical photographs. Surveyor is part of NYPL’s NYC Space/Time Directory, a two-year effort to combine the Library’s collections of photos, maps and other historical sources and datasets and make exploring New York City’s urban history more accessible—across space and time. Knowing the locations where our photos were taken allows us to juxtapose our historical maps with our photo collections, and enables us to create new interactive map viewers and search interfaces that allow our patrons to find historical addresses, buildings and businesses, and more easily connect them with photos and maps of the same moment in time, and location in the city.

If you’re interested in New York City’s history, try out Surveyor, and help us put our photo collections on the map!