Spatial Thinking in Planning Practice: An Introduction to GIS

43 oding address-referenced population data is one of the Census Bureau’s key responsibilities. However, as you may know, it is also a very popular capability of online mapping and routing services. In addition, geocoding is an essential element of a suite of techniques that are becoming known as “business intelligence.” We will look at applications like these later in this chapter, but, !rst, let’s consider how the Census Bureau performs address geocoding. ADDRESS GEOCODING AT THE US CENSUS: PRE(MODERNIZATION Prior to the MAF/TIGER modernization project that led up to the decennial census of 2010, the TIGER data- base did not include a complete set of point locations for U.S. households. Lacking point locations, TIGER was designed to support address geocoding by approximation. As illustrated below, the pre-modernization TIGER database included address range attributes for the edges that represent streets. Address range attributes were also included in the TIGER/Line !les extracted from TIGER. Coupled with the Start and End nodes bounding each edge, address ranges enable users to estimate locations of household addresses (Figure 7.1). Figure 7.1: How address range attributes were encoded in TIGER/Line !les. Address ranges in contemporary TIGER/Line Shape!les are similar, except that “From” (FR) and “To” nodes are now called “Start” and “End”. Souce: U.S. Census Bureau 1997. Here’s how it works. Figure 7.1 highlights an edge that represents a one-block segment of Oak Avenue. "e edge is bounded by two nodes, labeled “Start” and “End.” A corresponding record in an attribute table includes the unique ID number (0007654320) that identi!es the edge, along with starting and ending addresses for the le$ (FRADDL, TOADDL) and right (FRADDR, TOADDR) sides of Oak Avenue. Note also that the address ranges include potential addresses, not just existing ones. "is is done in order to future-proof the records, ensuring that the data will still be valid as new buildings and addresses are added to the street. "is chapter text has been compiled from the following web links that holds information with CC copyrights: use and share alike. Chapter 7: Geographic Considerations in Planning Practice