Chapters 1, 2, and 5 introduced the concepts of location specification, coordinate systems, and the methods used to determine positions anywhere on Earth. Together, these concepts provide the ability to easily acquire and organize vast amounts of spatial data. In Chapter 3, we saw how these data can be visualized in the form of thematic maps, with several examples that relied on or were enhanced by data from the US Census Bureau.
The US Census Bureau is well-known for collecting neighborhood statistics and social data. In addition to social and economic data, the Census is also responsible for another important product that underpins a wide array of geographical analysis and mapping: the Topologically Integrated Geographic Encoding and Referencing (TIGER) database. Developed in a partnership between the Geographic Division of the US Census Bureau and the US Geological Survey (USGS), TIGER data are fundamental components of some of the nation’s largest and most used databases for transportation and for the delineation of political boundaries, congressional districts and census tracts. In preparation for the 2010 census, the Bureau conducted a database redesign project that combined TIGER with a Master Address File (MAF) database. MAF/TIGER enables the Bureau to associate census data, which it collects by household address, with the right census areas and voting districts. This is an example of a process called address-matching that will be described in more detail in Sections 6.1 and 6.6.
By the end of this chapter, you will gain familiarity with TIGER data as well as the concepts of topology, geocoding, and map-based routing. You will also learn about the geographic entities on which these products and processes rely.
Students who complete Chapter 6 should be able to
- explain how geometric primitives in MAF/TIGER are represented in TIGER/Line Shapefile extracts;
- define topology and explain why and how it is encoded in TIGER;
- understand what address geocoding is and how it works;
- describe how TIGER/Line files and similar products can be used for applications within transportation, routing, and business applications.