NYCityMap Geocoding and Map Rendering

The process of using an address or intersection to get geographic coordinates for the purpose of mapping a location is known as geocoding.  NYCityMap relies on the Department of City Planning’s mainframe-based Geosupport  system (Geosupport was developed specifically for New York City in the 1980’s and has evolved over time to handle the many NYC addressing anomalies including Queens hypenated address – well before others could, out-of-sequence addressing and Edgewater Park.) for basic geocoding functionality.

There are different methods that can be employed for geocoding an address.   One approach, often called fall-back or cascade geocoding, attempts to find a match using the highest degree of precision and moves to lower precision methods until a match is found (if one exists).  NYCityMap employs a fall-back approach using Geosupport for the individual geocoding requests (i.e., passes) and then queries the spatial data to render the results on a map.  This results in different types of maps being rendered after submitting an address search.

The first pass tries to match an input address against the actual address(es) associated with a tax parcel or building.  The unique identifiers for these features are returned as part of a successful geocode.  These identifiers are then used to query the database to find a match and render the results on the map.  If a building match is found, the building is highlighted in the resulting map (see example below) and building-level information is available.

Building Geocode

If a building is not found but a tax parcel is (pass two), a star representing the center of the tax parcel is placed in the resulting map (see example below).

Parcel Geocode

The second pass attempts to match the address against the theoretical range of addresses along a block (a street between two cross streets).  This method interpolates between the highest and lowest addresses for each side of the street.  For example, Maiden lane between Nassau and William Streets has the following address rages:

  • North side of the street; low = 28 and high = 62
  • South side of the street; low = 29 and high = 65 and 1 Federal Reserve Plaza
This method results in a star placed at the interpolated location between the high and low addresses as shown in the example below.  This method is included to ensure the highest hit rate.  An address may be missing from a database or a person may not have indicated the correct house number. For this method, building and property level information is not available.

Address Range Geocode

NYCityMap 10.0 Release Notes

Performance Enhancements

We’re excited to announce release 10.0 which contains a lot of performance enhancements. With this release we attempted to reduce the initial map load time as much as possible. To accomplish this we:

  • converted our tool icons to sprites
  • added cache-control headers for browser and proxy level caching of files which change infrequently
  • created new domain names for serving map tiles from multiple domains for faster simultaneous download
  • added more caching of thematic data on the server-side, this benefits applications like SCOUT, 311 SRMap, and Performance Mapping Report
  • reduced search time for retrieving elected officials

Health Facilities

We’ve added the locations of a few health facilities to NYCityMap.  You can find them all in the Health Facilities group.

New Basemap Tiles

We’ve released a new set of basemap tiles.  Some improvements to the tiles include:

  • update to most recent version of LION (find out more information about LION from DCP’s Bytes of the Big Apple)
  • update to most recent building footprint data
  • display of additional park features
  • display of additional street labels at certain scales

Park Tile Before

Park Tile Now

Street Tile Before

Street Tile After

MapPLUTO 10v2

Also in this release we have upgraded from MapPLUTO 10v1 to 10v2. MapPLUTO is available from the NYC Department of City Planning, you can find out more information from their Bytes of the Big Apple website. NYCityMap uses MapPLUTO to provide much of the building information that you see when you search for an address or identify a building on the basemap.

DEP Green Infrastructure Map

In September of 2010 NYC DEP (Department of Environmental Protection) released the NYC Green Infrastructure Plan. According to the Executive Summary, “This Green Infrastructure Plan presents an alternative approach to improving water quality that integrates green infrastructure, such as swales and green roofs, with investments to optimize the existing system and to build targeted, smaller-scale ‘grey’ or traditional infrastructure.”

A major component of the web strategy is to implement a mapping application to show Green Infrastructure projects. This application can be accessed through the ‘Other Themes’ menu on NYCityMap or by clicking here.