Geographic Information Systems TIGER Data

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

2 Census Units ► Census tracts ► Block groups ► Blocks

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

2 Census Units ► Census tracts

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

Block groups R Brancoto, SUNY Buffalo

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 - The last three are consecutive and unique within a block group

Census Units.. County Census tract Block group Block

3. GBF/DIME Files ► Geographic Base Files (GBF) ► Dual Independent Map Encoding System (DIME) ► 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

4 Vector (1) Non-Topological Structure Storing coordinates of two polygons: and Polygon x 1, y 1 ; x 2,y 2 ; x 3,y 3 ; x 4,y 4 ; x 5,y 5 ; x 1,y 1. Polygon x 1, y 1 ; x 6,y 6 ; x 7,y 7 ; x 2,y 2 ; x 1,y 1. (x1, y1) (x2, y2) A B

4 Vector (2) Topological Structure Storing coordinates of two polygons: and Line 1 x 1, y 1 ; x 2,y 2 ; x 3, y 3 ; x 4, y 4 ; x 5,y 5 ; Line 2 x 1, y 1 ; x 5,y 5 ; Line 3 x 5, y 5 ; x 6,y 6 ; x 7, y 7 ; x 1, y 1 ; Polygon Line 1, Line 2 Polygon Line 2, Line 3 (x1, y1) (x5, y5) Line 1 Line 2 Line 3

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

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 - a tabular form of demographic, social, economic statistics statistics - a GIS form - a GIS form ► Aggregated information is available at the block group level, few at the block level

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

TIGER..

► American Community Survey ► An ongoing statistical survey that samples a small percentage of the population every year ► 1-year, 3-year, and 5-year estimates ta_users/estimates/ ta_users/estimates/

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

Address Matching (line data)

Address Matching..

Network Analysis Shortest path routines (line data)

Network Analysis.. Salesperson Problem (line data)

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

Districting Delineation Political redistricting (polygon data)

Readings ► Chapter 3

4. TIGER

GBF/DIME Files..