NYC Building Footprints

I have seen and received quite a number of emails, and have even seen applications that confuse MapPluto for a building data set. To clarify what the building footprint’s represent as well as to remove any confusion between the two very different data sets, I decided to write this post.

MapPluto is a compilation of City agency data at the tax lot (aka parcel) level produced and distributed by the Department of City Planning. A tax lot defines the basic unit of land ownership. Much has been written about MapPluto, so I do not intend to cover this data set in detail. However, it is important to understand that a tax lot can encompass multiple buildings.

A NYC tax lot uses Borough Block and Lot (BBL) as a unique parcel identifier. DCP compiles a variety of City data sets at the parcel level into MapPluto. One of the main data sources is the Department of Finance’s (DOF) Real Property and Assessment Data (RPAD). One of the attributes in RPAD is Number of floors, which is included in MapPluto as NumFloors. DCP defines this column in the metadata as being for “…the primary building on the tax lot, the number of full and partial stories starting from the ground floor.” This is due to the fact, as previously stated, that there can be multiple buildings on a tax lot. Since only one value is possible, DCP elected to go with the number of floors of the ‘primary’ building.

An example of a tax lot with multiple buildings is the community of Breezy Point, Queens. Originally a gated community of summer bungalows that are now permanent homes, Breezy Point spans 12 tax lots and encompasses 3,017 buildings. one of the parcels (BBL 4163400050) includes 424 buildings and has a value of 1 for the number of floors. Although the houses in Breezy Point are of similar housing stock, the number of floors is for the ‘primary’ building and thus not an exact figure. Another common example are NYC Housing Authority (NYCHA) developments. Although buildings within a development are often the same number of floors, this is not always the case.

In general, it is the responsibility of the person working with the data to read the metadata to get an understanding of the data and its limitations and constraints. There are cases where values are estimated, imputed or no longer actively maintained. In the case of MapPluto, building height applies to only one of potentially many buildings on a tax lot. This is not an error but a limitation of the data.

Building Footprints
Building footprints represent the ground-level perimeter outline of a building (i.e., footprint) greater than or equal to 400 square feet and greater than or equal to 12 feet in height unless they were previously captured and have a Building Identification Number (BIN). The purpose for the size and height constraint is to prevent the capture of non-buildings (e.g., containers, tents), which we have seen in the past. The specifications to which built features are captured and which are not can be found in the metadata.

The building footprints include ground and roof height elevations. These values are in feet and are derived photogrammetrically using stereo imagery, LiDAR and a TIN model.

There are cases where there will be no value in these columns. The reason for this is how the building footprints are maintained. To understand this, we need to revisit the past.

The building footprints were first captured as part of the first NYC Planimetrics in 1997 based on 1996 imagery. The NYC Planimetrics came to be called NYCMap. An excellent article on this effort can be found in the New Yorker (unfortunately a subscription is required to access the full article). In the beginning there was no plan for the periodic update of the planimetrics. Since 2006 the planimetrics have been updated on a four-year cycle.

Utilizing the Department of Buildings (DOB) permit data (new construction, major alterations and demolitions), it was determined that the building footprints could be updated on a more frequent basis. Since 2004 the buildings have been updated regularly and since the NYC Open Data Portal launched have been updated on a quarterly basis. These updates are done on-screen using heads up digitizing. Since these updates are not done photogrammetrically elevations values are not available and thus not in the database. With each planimetric update, buildings that are digitized on-screen are replaced with photogrammetrically-captured buildings and elevation values are assigned.

Lastly the Building Identification Numbers (BIN) assigned by DCP are inserted into the corresponding building footprint. The BIN is the unique identifier used by City agencies to identify buildings. Many agencies utilize the BIN to associate additional data to a building. BIN is returned by Geoclient API geocoding service provided by DoITT.

Make your own map of NYC

So you want to make a map of NYC. You are familiar with the NYC Open Data Portal but have had some difficulty in finding all the data you need. You have the requisite software to construct the map (e.g., QGIS, ArcGIS, MapBox Studio, etc.) and the basic skills to do so. Perfect, read on.

This post is intended to provide a single source for the map ingredients. It is not intended to be the map cookbook. It’s up to the reader (i.e., mapper) to decide on data to include, colors, symbols, labels, fonts, etc.

NYC Planimetrics

The table below lists NYC DoITT geospatial data on the Open Data Portal and provides a very basic description of each data set. For more detailed information, see the included metadata. The table is grouped into core basemap features and other DoITT data.

The first grouping of data comprises the data used to construct the above map. These data are referred to as the planimetrics (aka NYCMap). Planimetrics are features captured from aerial photography and represent the City’s basemap. These features are updated on a four year cycle. Most but not all features are provided to the public. Utility structures is one that is not due to security concerns. For an historical perspective and to see how far we have come, read the following article on NYCMap. *Note the full article requires a subscription.

The second group represents other NYC DoITT data that may be of interest but is not necessary for producing a basemap. Some of these data are maintained directly by DoITT and others are compiled from agency sources. We do our best to keep these data current.

The last group includes notable geospatial data sets not managed by DoITT and agency sites where spatial data can be found.

Feature Name Notes/Alternate name Download URL
DoITT Boardwalks Boardwalks
Building footprint Permiter of base of building with height
Contours Two-foot contours
Hydrography Water bodies
Hydrography Structures Manmade features at the waterfront
Medians Physical separation between travel lanes.
Miscellaneous Structures Billboards, sign gantrys, etc.
Open Space City and Non-City parks and fields
Parking Lots Paved parking areas
Pavement Edge Perimeter edge of pavement
Retaining Walls Where elev difference >= 10 feet
Roadbed Roadway (polygon)
Sidewalks Sidewalks in the right-of-way
Shoreline features NYC shoreline
Swimming pools Inground only
Additional DoITT Spatial Data
Address Points Point representing addresses.
Citywide Street Centerline CSCL; includes Bike lanes
Digital Elevation Model One-foot DEM
NYC Wi-Fi Hotspot Locations Open and fee-based public wifi
After-School Programs City-funded programs
Agency Service Center Walk-in service centers
Greenthumb Community garden program
Business Improvement Districts BIDS
Landmark Interiors Designated landmark interiors
Landmark Points Designated landmarks
Historic Districts Designated historic districts
NYCHA Developments New York City Housing Authority
Zip Code Boundaries Zip code polygons
Notable Non-DoITT Spatial Data
Digital Tax Map DOF tax map; inlcudes blocks, lots, air rights, etc.
Bytes of the Big Apple Various data sets including MapPLUTO
Dept. of Transportation Various data sets & feeds

Every effort will be made to ensure the above table is complete and the links are current. If you find an error or omission, please feel free to add a comment below to let us know. Lastly, check back periodically as this table will be expanded as newer data sets are published.

Happy mapping!

NYCityMap version 3.0

We are in the midst of planning and developing the release of NYCityMap 3.0. The current version, launched in 2010, has had a good run but is showing its age and is in need of a refresh.

As we often try to gather feedback from our audience, this blog post is intended to lay out the basic objectives and to solicit feedback. Follow up posts will be more targeted towards extracting specific input through the use of polls and other online tools.

The basic objectives of the update project are:

  • Responsive design supporting mobile devices;
  • Simplify user interface/presentation of data;
  • Include appropriate existing functionality;
  • Ability to easily update and publish data (for us);
  • Provide a gateway to other mapping applications within NYC;
  • Move away from custom code and leverage a more complete open source solution.

Below are some preliminary screens using OpenLayers 3.0 with tiles generated from ArcGIS Server.

Feel free to comment on this post and send along your feedback on how you would like to see NYCityMap evolve.

NYC Crime Map

On December 8, 2013 New York City launched the NYC Crime Map. In collaboration with the NYC Police Department, the NYC Crime Map was developed in-house by DoITT GIS staff using Google’s Maps API, Places API and Maps Engine.

The application went through multiple rounds of intensive code reviews with Google engineers and rigorous regression testing by DoITT Quality Assurance staff. Map Engine Query Per Second (QPS) and Query Per Day (QPD) limits were increased to accommodate the expected high volume of traffic. These measures were taken to ensure a smooth release and positive experience for the users.

The application follows a responsive web design approach and is therefore optimized for most modern smartphones, tablets and desktop computers. The screenshots below demonstrate the layouts in a desktop browser and iPhone.

Crime Map

Crime Map in desktop.

Crime map in iPhone.

Crime map in iPhone.

To protect privacy, crime data are located at the nearest intersection of a crime or the midpoint of a City block (approximately a street defined by two intersecting cross streets) for crimes occurring at a discrete addresses. For a detailed description of the data methodology, see the About page.

Crime can be visualized as graduated points, shaded precincts (i.e., choropleth) or a heat map. The graduated point view renders the data as points varying in size by the frequency of crimes at that specific location. In this way, locations with greater occurrence of crime will have a larger point. The precinct map aggregates the crime to the precinct level and normalizes the data showing aggregate crime rates (crimes per 1,000 people). The precinct view provides a city wide view of the data and allows for comparison of crimes across the different precincts that make up NYC. The heat map uses the Google Map API heatmap function to show the relative concentration or intensity of crime.

Local Law 39, passed by the City Council in May,2013, was the basis for the interactive crime map. This legislation provides the public with a more detailed view of crime within NYC than previously possible. As per the legislation, crime data is available for the current year and previous year and is aggregated by month, year to date and full year. The data will be updated monthly as it is received.

Press release.

Interface changes

The previously mentioned NYCityMap interface changes are now live. These changes reflect usability improvements and address feedback received. The result is the preservation of existing functionality while streamlining the user interface. The changes are:

Addition of an Advanced tool. Within this are the previous tools that existed over the base map.

Advanced Tool

Replacing the slider with Map Type tool. Many users were confused by the slider and the ability to toggle between a cartographic map (Map) and the numerous years of aerial photography. All of these base maps still exist but are are now within the Map Type tool. The base map selected is shown by a check next to the entry.

Map Type

Where is the identify tool?

The current release of NYCityMap includes interface updates and addresses issues resulting from the recent update of Chrome (version 29). The interface changes were a result of feedback received and are intended to improve the user experience.

The identify tool was removed; however the functionality still exists. The default tool (Pan) now handles this function similar to Google and Bing Maps. On single left click of the mouse, the tool identifies map features provided the user is zoomed enough to see the feature being identified. On left mouse hold the tool pans the map.

The code changes required due to the Chrome update were related to Dojo widets employed by NYCityMap. These widget were not rendering in Chrome properly. To those who were impacted by this issue, we apologize for the inconvenience. We had made the code changes and were already through testing and ready for release when the Chrome issue struck, We therefore released both changes together.

Well the story does not end there. We have since received feedback from some of our clients critical of the interface changes. We agreed with the feedback and have decided to make additional enhancements as follows:

  • Remove the Pan tool entirely. This will be the default tool (pan/identify/zoom);
  • Add zoom one level on left double-click of the mouse;
  • Add an Advanced Tools button and place within the drag zoom, measure, save map and email a friend tools;
  • Change the Show Aerial Photo tool to a button title Map Type. On click menu items will show the different Aerial Photography years.
  • Change the drag zoom and measure tools to single action (i.e., after single use the tool defaults back to pan/identify/zoom.

These changes are underway and we expect to release these barring any unforeseen issues by the end of the month.