Address Geocoding - Introducing Geographic Information Systems with ArcGIS - page 575

Address
Geocoding

OVERVIEW

A Second Fundamental Way of Defining Location

As discussed in detail earlier, a location on the surface of the Earth may be referenced in a spherical
coordinates system by a ray, emanating from the center of the Earth, defined by an angle of latitude
measured from the equator and an angle of longitude, measured from the prime meridian. This method
is “perfect” in that no error is introduced by the system itself; our accuracy is limited only by our ability
to measure. Latitude and longitude descriptions may be applied anywhere on Earth. (I also discussed
earlier how these two angles may be converted into myriad other pairs of coordinates through processes
of projection.)

A large part of the Earth that is most interesting to us consists of human-made infrastructure. Almost
always, such infrastructure includes streets and buildings. Further, the most usual way to describe a
location in such areas is with a street address. Such an address is a text string: a sequence of letters,
numbers, and other characters.

Outside of all addresses being text strings, addresses appear in a wide variety of formats. Some
examples: 15

26376 Alpine Lane, Twin Peaks, CA 92391, USA

76-20 34th Avenue, Jackson Heights, Queens, NY 11372, USA

305 W 100 S, Salt Lake City, UT 84119, USA

N84W 16301 W Donald Ave, St Charles, IL 60175, USA

Rua Aurora 735 01209001 Sao Paula, Brazil

Wendenstrasse 403, 20537 Hamburg, Germany

Such addresses are usually quite precise—locating a structure to within several meters, if you have a
good map of the area. By themselves, however, they tell us nothing about the location with respect to
most other locations, except perhaps for other structures located on the same street. For purposes of
mapping and analysis, we often want to turn addresses such as these into latitude-longitude coordinates,
or other coordinate pairs.

15 Courtesy of Geocoding in ArcGIS, published by Esri.