Address Matching (Geocoding)
Street addresses are the most common form of locational information. Yet an address is merely text information, containing a house number, street name, direction, and zip code. The GIS needs a mechanism to transfer this text information to calculate geographic coordinates before an address can be displayed on a map. Address geocoding is the process of linking an address to a physical location on the Earth. To do so, the GIS associates addresses stored in a tabular file with a spatial data set which has addresses, usually a street centerline file. The GIS then uses the coordinates of the street features to calculate and assign coordinates to addresses in the file. The result is a new spatial data layer of point locations representing the addresses from the file.
Address matching was used to create the ARC/INFO coverage of medical facilities shown in the figure below. A comma delimited text file containing the name of the facility, address, city, and zip code was imported into the GIS and address matched against the county street centerline file. In order to successfully match, the address street name must be spelled the same in both files and the street number must be within the address range valid for its particular street. Addresses that do not match are dumped into a rejects file which can later be examined by the user. In this project, a 98% match was achieved.
Other Types of Spatial Analysis
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