A geocoding service is a piece of software designed to connect textual address information with spacial geographic coordinates. These units are then converted into latitudinal and longitudinal data points on a map. With the rise in popularity of search engines and global positioning systems (GPS), geocoding has become an increasingly popular way to find the precise location of nearly any place in the world. There are three major methods that a geocoding service typically employs: address interpolation, postal code interpolation and boundary interpolation.
Address interpolation refers to the process by which a table of location names and their corresponding street addresses are mapped to positional information in a database. These points are then displayed on an interactive map using geotagging techniques. The positional information takes the form of address ranges within a particular street block. Through interpolation, an address is then placed in its appropriate designation on a street.
This process can be viewed as one of the more accurate methods related to a geocoding service. The accuracy of address interpolation lies in the fact that exact addresses are given, making it easier to find the matching latitudinal and longitudinal data. Even in rural areas, address interpolation is able to accurately pinpoint the location of a specific place as long as an actual street address — not a post office box address — is provided.
Postal code interpolation is the process by which a set table of location names and their postal codes are matched to the latitudinal and longitudinal positioning of a center data point. Interpolation allows for a unique postal code to correspond with the various coordinates found within the boundary of the postal code area. This method is most accurate in urban centers. In rural areas, results are not very accurate because postal code areas tend to be larger and more sparse, making it difficult to assign a place to its actual location on a map.
Boundary interpolation is the form of geocoding service related to estimating the location of a particular place using spatial analysis. When boundary data is provided in a table of latitudinal and longitudinal values, a location with similar boundary data can be mapped. This method of interpolation is the least accurate because it usually identifies a number of places with the exact same data point within boundary lines. In this way, the unique location of a single place is obscured, converting it into a shared data point for a number of different places.