I give the city an enormous amount of credit for the GIS data that they make available online. Unfortunately, the city’s love affair with Esri’s ArcGIS means that its spatial reference system (SRS) can be difficult to identify.
Fear not, however, as a quick trip over to one of my favorite websites ever, spatialreference.org, can help you find a corresponding EPSG code. The available conversions are invaluable for anyone interested in geospatial data. Simply give the site the contents of your .PRJ file or the projection’s well-known text (WKT) and you will get back that magical identifier.
Ah, and if you’re looking for the reference system that New York City usually uses then you’re probably looking for EPSG:2263