Winter 2017

Efficient Geocoding

By Mike Price, Entrada/San Juan, Inc.

Public safety organizations rely on reliable, repeatable incident mapping of address-based data. Some agencies have created in-house geocoding using locally developed E911 points and street files. Other agencies subscribe to location-based services that use commercially-provided street data. A typical fire/emergency medical service (EMS) provider could respond to 100 to 300 incidents per one thousand residents which might result in 20,000 incident responses or more in one year.

This total might include multiple responses to the same house, convalescent care facility, or large apartment complex. Since one address may be involved in many responses, it is not necessary to geocode each response record. Instead, street addresses may be summarized which creates a much smaller address set. By geocoding the summary set, joining longitude and latitude coordinates back to the parent incident table, and creating and saving an XY response data set, many points can be mapped by geocoding many fewer records. As always, the key to success involves clean, standardized address assignments.

Esri provides several ways to geocode addresses with online services. For several years, ArcGIS Online has included an ArcGIS World Geocode Service that provides an effective multiple field geocoding service. It includes the ability to edit and re-geocode complex addresses. ArcGIS Pro includes many tools to perform custom and standard ArcGIS Online World Geocoding tasks.

Online World Geocoding requires a current ArcGIS Online subscription and uses service credits. Forty credits are needed to geocode 1,000 addresses. A single ArcGIS Online account includes 100 annual service credit.

Two exercises have been developed to teach a simplified workflow for posting more than 1,000 incidents to a map in both ArcGIS Pro and ArcGIS Online. The sample data for these geocoding exercises was provided by the Kent Fire Department in Washington state for two response districts in downtown Kent.

The Kent Fire Department has used address geocoding for many years and has applied a current, standard addressing schema. The addressing schema is referenced in National Fire Protection Association Standard 950 Standard for Data Development and Exchange for the Fire Service and is supported by the Federal Geographic Data Committee (FGDC) in FGDC-STD-016-2011, United States Thoroughfare, Landmark, and Postal Address Data Standard. You can read these documents to learn more about addressing standards.

The first exercise, "Efficient Geocoding with ArcGIS Pro," ran in the winter 2017 issue of the print edition of ArcUser. The second exercise, "Optimize Online Geocoding," available only in the online edition of this issue, uses ArcGIS for Desktop with ArcGIS Online.