Resources for developers about how to use our open data endpoints.

ESRI

{Explain public ArcGIS REST Services}

A common operation while working with open data is geocoding. Geocoding is a process to turn a text address (2 Woodward Avenue) into coordinates which can be plotted on a map (42.329543, -83.043720) or a parcel identifier that can be used to join to other datasets (01004068-86).

The city makes available three geocoders:

• Address point
• Matches an address input against a table of discrete address points, called the geocoder's reference dataset. Returns a parcel number and geographic coordinates for the center of that parcel
• Pros: address points in the reference dataset can be related to a parcel
• Cons:  you need to have good input to return a match - you can get away with small typos in the street name, but not much more than that
• Street centerline
• Matches an address input against a layer of city streets which have an address range attached; returns geographic coordinates for where your input address should exist along the street
• Pros: you can match addresses which don't exist in the address point table used by the address point geocoder
• Cons: the coordinates returned will be inexact and there will not be a parcel number attached
• Composite (we recommend using this one!)
• Accepts address input, parses that input, checks first for a match against the address point geocoder and returns that match. If there’s not an address point match, returns a street centerline match

Read this blog post for a full introduction to geocoding and more detailed examples of how to utilize the City’s geocoders in your workflow.