Spatial Thinking in Planning Practice: An Introduction to GIS

37 munity Survey that surveys a representative sample of households on an ongoing basis. Every month, one house- hold out of every 480 in each county or equivalent area receives a survey similar to the old “long form.” Annual or semi-annual estimates produced from American Community Survey samples replaced the SF3 data product in 2010. To protect respondents’ con!dentiality, as well as to make the data most useful to legislators, the Census Bureau aggregates the data it collects from household surveys to several di#erent types of geographic areas. SF1 data, for instance, are reported at the block or tract level. "ere were about 8.5 million census blocks in 2000. By de!ni- tion, census blocks are bounded on all sides by streets, streams, or political boundaries. Census tracts are larger areas that have between 2,500 and 8,000 residents. When !rst delineated, tracts were relatively homogeneous with respect to population characteristics, economic status, and living conditions. A typical census tract consists of about !ve or six sub-areas called block groups. As the name implies, block groups are composed of several census blocks. American Community Survey estimates, like the SF3 data that preceded them, are reported at the block group level or higher. "e unit types are organized with each higher type composed of some number of the lower type as outlined above for blocks, block groups, and census tracts (Figure 4.16). Figure 4.16 Relationships among the various census geographies. Source: U.S. Census Bureau, American Fact- Finder. http://fact!nder2.census.gov/faces/nav/jsf/pages/using_fact!nder5.xhtml "is chapter material has been collected from the following web links that holds information with CC copy- rights: use and share alike. https://www.e-education.psu.edu/geog160/c3_p14.html https://www.e-education.psu.edu/geog482fall2/c3_p16.html https://www.e-education.psu.edu/geog482fall2/c3_p17.html Discussion Questions 1. In what ways do local planners rely on US Census data? 2. How does a pie chart and a bar/column chart di#er? What are their visual advantages and disadvantages Chapter 4: Mapping People with Census Data