What is a geocoder? It’s a utility that takes a textual representation of a street address and finds its geographic position using data such as street centerline geometries. The textual representation of an address often goes through a standardization process called address normalization or address standardization that takes the textual representation and breaks it into its component parts, such as street number, street name, suffix, and so on, and ensures that the same type of pieces are always represented in the same way. It is this standardized address that geocoders work with. Geocoders generally return the longitude and latitude.
In this chapter, we’re going to focus on the PostGIS geocoder specifically designed for TIGER. The TIGER acronym stands for Topologically Integrated Geographic Encoding and Referencing, and it’s a geospatial database maintained by the US Census Bureau. The structure is topologically defined with edges, nodes, and faces very similar in structure to how the postgis_topology extension structures data. The database encompasses key features of geographic interest in the entire United States, including political boundaries, lakes, reservations, major and minor roads, rivers, and so on.