1. Geographic Information Systems
Census Data

2. 1 Street Unit Street segment
- The range of addresses that run along a street from one intersection to the next intersection
Address range
- The range between the lowest possible house number at one intersection and the highest possible house number at the other intersection

3. 2 Census Units
Census tracts
Block groups
Blocks

4. 2 (1) Census Tracts
Defined by the U.S. Census Bureau for statistical reporting of demographic, economic, and other data
The boundaries follow major streets or natural features
Population in each tract is approximately 4,000 regardless of its size
Census tracts are numbered consecutively and unique within the jurisdiction

5. 2 Census Units
Census tracts

6. 2 (2) Block Groups Comprise a population of approximately 1,500
Boundaries coterminous with census tract boundaries

7. Block groups R Brancoto, SUNY Buffalo
                

8. 2 (3) Blocks Smallest geographic area formed by street segments
Coded by a 4-digit number
- The first one represents the block group
- The last three are consecutive and unique within a block group  

9. Census Units ..
County
Block
Census tract
Block group

10. 3. GBF/DIME Files Geographic Base Files (GBF)
Dual Independent Map Encoding System (DIME)  
A data format used by the U.S. Census Bureau to encode street network and related data for the 1980 Census.
It covers only the metropolitan areas
- DIME was replaced by TIGER in 1990 census

11. 4 Vector (1) Non-Topological Structure
Storing coordinates of
two polygons: and
Polygon
x1, y1; x2,y2; x3,y3; x4,y4; x5,y5; x1,y1.
x1, y1; x6,y6; x7,y7; x2,y2; x1,y1. A
(x1, y1)
(x1, y1) 1 2 1 2 B
(x2, y2)
(x2, y2) 1 2

12. 4 Vector (2) Topological Structure
Storing coordinates of two polygons: and
Line 1
x2,y2; x3,y3; x4,y4; x5,y5; x1,y1;
Line 2
x1,y1; x2,y2;
Line 3
x1,y1; x6,y6; x7,y7; x2,y2;
Polygon Line 1, Line 2
Polygon Line 2, Line 3 1 2
(x1, y1)
(x1, y1)
Line 1 1
Line 2 2
Line 3
(x2, y2)
(x2, y2) 1 2

14. 4. TIGER
Topologically Integrated Geographic Encoding and Referencing Files (TIGER)
Developed by the U.S. Census Bureau for 1990 census
The spatial and attribute processes were combined into one system
A single seamless data set that covers the entire country
Topologically structured

15. TIGER Geographic Features
A combination of DIME and 1:100,000 Digital Line Graph
Uses geographic coordinate system
Two types of data:
- a tabular form of demographic, social, economic
statistics
- a GIS form
Aggregated information is available at the block group and tract level, few at the block level

16. TIGER Geographic Features ..
GIS data are available as both polygon data and line data
The polygon data contain the population information in tracts, block groups, and blocks
The line data contain streets and utility lines information
The data have spatial locations, attributes, and topology

17. TIGER ..

18. TIGER .. American Community Survey http://www.census.gov/acs/www
An ongoing statistical survey that samples a small percentage of the population every year

19. TIGER ..
1-year estimate for areas with a population of at least 65,000, suitable for study of short-term changes at medium to large geographic scales.
5-year estimate for all areas down to the block geographic scale, suitable for study long-term changes at small scales

23. 4. TIGER

24. TIGER ..

25. 5. Applications of TIGER Data
Address matching
Network analysis
District delineation

26. Address Matching (line data)

27. Address Matching ..

28. Network Analysis Shortest path routines (line data)

29. Network Analysis .. Salesperson Problem (line data)

30. Network Analysis .. Location allocation (Line and polygon data)

31. Districting Delineation
Political redistricting (polygon data)

32. Readings
Chapter 3

33. http://ftp2. census. gov/geo/maps/special/HurKat/Katrina_Reference_v2