Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition

TIGER/Line Files

Determining geographic coordinates from addresses is a tall order. Let’s begin by restricting ourselves to the United States and the forms of address used there. You have already met TIGER/Line files, developed by the Bureau of the Census. If the terms behind the acronym17 TIGER leave you confused, consider the predecessor description of such files: DIME, standing for Dual Independent Map Encoding. The idea behind “dual” is this: Each record in the file contains two geographic references. One is a range of address; the other is latitude-longitude coordinates. So this sort of file ties together (a) locations specified by text strings with (b) locations that are specified by geographic coordinates.

Each record in the TIGER file specifies a geographic line (called a chain). For streets in urban and sub urban areas, the chain usually represents a single block. At the ends of chains are intersections. See Figure 9-16.

FIGURE 9-16

Each record also contains the street name (Ninth, Jenkins, etc) and street type (Lane, Drive, etc.) together with any prefixes and suffixes (NW, E, and so on). The referenced line has a beginning point and an ending point. Each such point is defined by a latitude and longitude pair, in the NAD 1983 geographic (latitude, longitude) coordinate system. Further, at the beginning of each line, two structure numbers (street address numbers) are ...