Does Geographic Data Change?

Funny you ask because Geographic data is always changing

Information is [not] necessarily wrong, but it is accurate based on certain assumptions, and at a particular place in time.

When a location such as an address is provided to NYC311 by a complainant, a geocoder built by a team at the NYC Department of Information Technology and Telecommunications (DOITT) is used to supply the latitude and longitude of that location, as well as additional locational attributes. This information may also be supplemented with a geodatabase of additional features spatially joined based on the output of the geocoder.

Though the NYC311 data is updated daily, the underlying data which is used to fill some of its columns is not. Nothing in the table is in “real-time” and as such it cannot be taken at face-value as fact. That is not to suggest that any of the information is necessarily wrong, but it is accurate based on certain assumptions, and at a particular place in time. This is particularly true for geographic attributes, whether those provided in the raw data or joined to it by a user. The NYC311 data contains complaints going all the way back to 2004, and various geographic features in New York City have changed over the course of the past decade and a half.

For example:

  • Some census blocks and tracts may have been updated after the 2010 Census (and there may be new updates after the 2020 Census)
  • Tax lots, the "BBL" attribute in the data, may be merged or reapportioned on a daily basis by the Department of Finance (DOF)

However, internal updates by an agency are not shared daily with other agencies and can take time to appear in their databases. 

What's the point?

Even the coordinate values need to be given further consideration though. A simple map visualization of the data would demonstrate that some service requests are geocoded to the center of tax lots, and others are geocoded to a point in the middle of a street. These outputs are based on what type of location is provided by the complainant, and through which method the complaint was made. Thus, even something ostensibly as objective and “true” as a geographic coordinate in a given reference system is in fact still generalized and relative. The points along street segments in particular require further consideration. Street segments are assigned address ranges, and this information is maintained and updated daily by the Department of City Planning. When an address is fed into the geocoder, it calculates the location for the address along the segment based on the segment’s length and assigned range (e.g. for a segment which has an east to west range of 10 through 20 Broadway, 11 Broadway would be located by the eastern node, and 14 Broadway would be near the middle). It is possible though for a segment to have a much larger range than actual physical addresses associated with it. As a result, if a block has four physical addresses but is along a segment with a range of 100 addresses, the location of a complaint at one of those addresses may be placed near the start or middle of the segment even if the building itself is at the end of the block/street.

Summary Statistics

Categories for NYC311 Service Requests