Introduction to ArcGIS for Environmental Scientists Module 3 – GIS Analysis Address Geocoding

Address Geocoding - 1 Introduction to ArcGIS Objectives Learn what data and processes are required to convert street addresses to map coordinates

Address Geocoding - 2 Introduction to ArcGIS Components A table with street addresses to be mapped An Address Locator to match addresses to reference data Reference data, usually streets, that contains features to which the addresses are matched Parcel-based reference data are thought to be more spatially accurate, but won’t necessarily result in more addresses being matched Zip code-based geocoding will produce a high match rate, but locations will be placed in center of a zip code.

Address Geocoding - 3 Introduction to ArcGIS Example Address table Reference data attribute table The address locator parses the street address into number, name and type to find a match in the reference data

Address Geocoding - 4 Introduction to ArcGIS Process For each address, a list of potential matches (candidates) in the reference data is generated Each candidate is scored between 10 and 100, where higher scores represent better matches Candidate with the highest score wins, if it is above a minimum user-defined threshold The output attribute table includes the match score and status: M = Matched, U = Unmatched or T = Tied Rematch unmatched and tied addresses Can be done in ArcMap or ArcCatalog

Address Geocoding - 5 Introduction to ArcGIS Data Quality Unmatched addresses, or addresses matched with low scores, are usually caused by errors in the address table or reference data – Misspellings (“Carelton” vs. “Carleton”) – Missing information (e.g. street type) – Outdated reference data (missing newer streets)

Address Geocoding - 6 Introduction to ArcGIS Rematching Addresses Used to match tied and unmatched addresses There are three ways to rematch addresses: – Automatically by lowering sensitivity or minimum match score in geocoding options  Can result in matches in wrong locations – Manually by examining unmatched and low score matched addresses and correcting errors – Manually by selecting location on a map

Address Geocoding - 7 Introduction to ArcGIS Interactive Rematching

Address Geocoding - 8 Introduction to ArcGIS Using Online Geocoding Services Address locator and reference data are located on the server You add the locator in ArcMap and provide the address table The service geocodes the addresses and creates an output feature class You may set the geocoding options and all rematching capabilites are available, as if the process were run locally