An address is simply a method used to describe a location. For geocoding purposes, it can be a street address, a place-name, or a location that is identified by a code. An address describes how to reference a location based on existing features in your geographic information system (GIS) database. In most cases, this description is relatively easy to understand. For example, if you needed to locate the street address 380 New York St., Redlands, CA, 92373 with the correct street data, it would not take you long to find the exact location. You might first find California, then find the city of Redlands. You might also use a postal code map and locate the region covered by the corresponding ZIP Code value. You would then locate the street and, finally, interpret where and on which side of the 300 block the address is located.
Just as you first narrowed your search to a specific region, found a particular feature, and interpreted a point, the computer is using the same process to assign a location to an address when geocoding.
As the illustration below shows, when finding a U.S. address, typically you find the state; then the city; and finally, the exact street.
Addresses have some specific characteristics. An address contains certain address elements and is presented in a range of formats. When geocoding, the address format is interpreted and address elements are identified and compared against elements stored in the address locator.
An address element is an individual component in the address, such as the house number, street name, street type, and postal code. Address elements help in the geocoding search, pinpointing an address to a particular location.
Addresses are represented in a wide range of formats. A common address format used in the United States consists of the following series of address elements: house number; prefix direction, prefix type, street name; street type, suffix direction; and zone information such as city, state, and ZIP Code.
In many areas, addresses are presented in different formats. One example of these alternative formats is the address format used in Queens, New York. In the mid-1920s, the Topographic Bureau of Queens unified the street names and implemented a hyphenated address style. The first number indicates either the north or west cross street. The second number indicates where on the block the building is located. Also as a general rule in Queens, avenues run east to west and streets run north to south. Queens also includes the neighborhood, or borough, where the address is located. This is a practice used in many parts of the world. While the address format used in Queens is not initially recognizable, the address format still contains the elements needed to assign it to a specific location.
Salt Lake City, Utah, also uses an alternative address format. When the streets were initially laid out in Salt Lake, the Latter-Day Saints temple was the center of the community. Roads in each direction from the temple were assigned a numeric name indicating how far they were from the temple, as well as directional value, indicating the direction from the temple that a street was located. The numeric prefix simply indicates the part of the road where the address is located. Again, while the address format differs from the common format, the basic address elements exist to locate each address.
Another United States example of address formats can be found in regions of Illinois and Wisconsin. In these regions, the address format includes a "grid zone" address element. A grid zone is simply a larger block or grid on which the address is located. The corresponding house numbers on the streets are assigned values based on the location and the particular street block. The grid zone value helps pinpoint the street number to a particular zone within the community.
International addresses can also be presented in a range of formats. For example, a common Brazilian address contains most of the basic address elements. However, they are arranged in a somewhat different pattern. Also, the particular state is not directly specified. However, it can be derived from the postal code or city. Due to some variations in language and culture, it might appear that certain address elements are being eliminated; for example, in a German address, the street name as well as the street type can be concatenated into one term.
Besides the common street addresses, a place-name such as Lincoln Center, Mount McKinley, or a ZIP Code can be considered as an address for geocoding purposes. Sometimes, finding a location by only the ZIP Code is a common practice, as an area that covers the ZIP Code can be identified.
While all of these addresses differ to some degree, some things remain consistent. Each address consists of one or several address elements, presented in a particular address format recognized by those in the region. Understanding that all addresses contain particular address elements will help determine the selection of an applicable address style and how an address should be matched.