Harvard Government 90dn Lecture 3
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Government 90dn Mapping the Census Lecture 3: More on GIS; Spatial Data Structures;TIGER Sumeeta Srinivasan [email protected] Reference: Unlocking the Census, Ch 2; TIGER documentation www.census.gov; Introduction to GIS (Huxhold); Geographic Information Systems and Science, Longley, Goodchild, et al.
Outline What is GIS? GIS Data types Raster vs Vector
Data structures TIGER data structure for address matching
Geographic Information Multidimensional Has volume Requires projection to flat surface Analyses require data integration Unique analysis methods
Geographic Information System (Definitions) Container of maps Computerized tools for solving geographic problems Mechanized inventory of geographically distributed features and facilities Method for revealing patterns and processes in geographic information
Geographic Information System Container of maps
Geographic Information System Mechanized inventory of geographically distributed features and facilities
Geographic Information System Computerized tools for solving geographic problems
dotdgis.dotd.louisiana.gov dotdgis.dotd.louisiana.gov/website/GIS-T2006.ppt
Geographic Information System Method for revealing patterns and processes in geographic information
Spills in Boston, Cambridge, Somerville Mean Population Weighted Center (close to intersection of Fenway and Forsyth in Boston)
Directional Ellipse for Population
Hazardous and Oil Spills Center (close to intersection of Main and Portland in Cambridge)
Directional Ellipse for Spills
Geographic Information System (Definitions) Container of maps Computerized tools for solving geographic problems Mechanized inventory of geographically distributed features and facilities Method for revealing patterns and processes in geographic information
Why Represent? “Almost all human activities require knowledge of the Earth” “Representations help us assemble far more knowledge than is possible on our own” “The world is infinitely complex but computer systems are finite. Representations must limit detail”
GIS Data Models Discretize Geographical Reality field view (regions) vs. object view (objects in a plane)
Data Model implies spatial sampling and spatial errors
Rasters and Vectors How to digitally represent phenomena conceived as fields or discrete objects? Field View: Raster Object View: Vector
“Real World”
Raster vs Vector Data Structure Raster Representation 0 0 1 2 3 4 5 6 7 8 9
1
2
3
4
5
6
Vector Representation 7
8
9
R T R R R
H
T
point line
R R R R R R R
T T T T
H
polygon
Lab Exercise 2 Step by step creation of data structures Point, line and polygon tables Topology tables
Topology in Data Structures Defined as the spatial relationships between neighboring features Implemented within data structure by defining: connectivity: Which arcs meet at a node? area definition: Which arcs make up the polygon? contiguity: Which polygons are on the left and right?
Lab Exercise 1 How to use TIGER data to match up Tuscaloosa school addresses?
TIGER Files Lines z
streets, railroads, rivers
Areas z
zip codes, census blocks, tracts, places, counties, etc.
Points landmarks such as churches, schools, and other cultural features represented in TIGER as points
z
Linear Address Matching (Streets) Urban street maps Four street address numbers ranging from low to high for each side of a street segment. Left_from 101
Left_to 199
Right_from 100 0105 0107
Right_to 198
Street_name OAK
100 101 (80.731, 40.025)
Oak St.
Type ST 198 199 (80.729, 40.025)
Address Matching Major Steps Schools file ID
Address
Class
1437
123 Oak St
A
402
333 Pine Av
A
855
18 Bay Dr
B
Address Matching Major Steps Schools ID
Address
Class
1437
123 Oak St
A
402
333 Pine Av
A
855
18 Bay Dr
B
Attributes of Streets Parity
Street_
From
To
Street
Type
Side
2
98
Oak
St
R
E
5950
1
99
Oak
St
L
O
5950
100
198
Oak
St
R
E
6011
101
199
Oak
St
L
O
6011
Address Matching Major Steps schools Address
Class
1437
123 Oak St
A
402
333 Pine Av
A
855
18 Bay Dr
Oak St 100
5950 Pine Av
StoreID
B
6011
101
199 123
Attributes of Streets Parity
198
Street_
From
To
Street
Type
Side
2
98
Oak
St
R
E
5950
1
99
Oak
St
L
O
5950
100
198
Oak
St
R
E
6011
101
199
Oak
St
L
O
6011
Converting Georeferences GIS applications often require transforming data so that they line up These are standard functions in popular GIS packages
Street addresses must be converted to coordinates for mapping and analysis Using geocoding functions
Outline What is GIS? GIS Data types Raster vs Vector
Data structures TIGER data structure for address matching
Geographic Information Multidimensional Has volume Requires projection to flat surface Analyses require data integration Unique analysis methods
Geographic Information System (Definitions) Container of maps Computerized tools for solving geographic problems Mechanized inventory of geographically distributed features and facilities Method for revealing patterns and processes in geographic information
Geographic Information System Container of maps
Geographic Information System Mechanized inventory of geographically distributed features and facilities
Geographic Information System Computerized tools for solving geographic problems
dotdgis.dotd.louisiana.gov dotdgis.dotd.louisiana.gov/website/GIS-T2006.ppt
Geographic Information System Method for revealing patterns and processes in geographic information
Spills in Boston, Cambridge, Somerville Mean Population Weighted Center (close to intersection of Fenway and Forsyth in Boston)
Directional Ellipse for Population
Hazardous and Oil Spills Center (close to intersection of Main and Portland in Cambridge)
Directional Ellipse for Spills
Geographic Information System (Definitions) Container of maps Computerized tools for solving geographic problems Mechanized inventory of geographically distributed features and facilities Method for revealing patterns and processes in geographic information
Why Represent? “Almost all human activities require knowledge of the Earth” “Representations help us assemble far more knowledge than is possible on our own” “The world is infinitely complex but computer systems are finite. Representations must limit detail”
GIS Data Models Discretize Geographical Reality field view (regions) vs. object view (objects in a plane)
Data Model implies spatial sampling and spatial errors
Rasters and Vectors How to digitally represent phenomena conceived as fields or discrete objects? Field View: Raster Object View: Vector
“Real World”
Raster vs Vector Data Structure Raster Representation 0 0 1 2 3 4 5 6 7 8 9
1
2
3
4
5
6
Vector Representation 7
8
9
R T R R R
H
T
point line
R R R R R R R
T T T T
H
polygon
Lab Exercise 2 Step by step creation of data structures Point, line and polygon tables Topology tables
Topology in Data Structures Defined as the spatial relationships between neighboring features Implemented within data structure by defining: connectivity: Which arcs meet at a node? area definition: Which arcs make up the polygon? contiguity: Which polygons are on the left and right?
Lab Exercise 1 How to use TIGER data to match up Tuscaloosa school addresses?
TIGER Files Lines z
streets, railroads, rivers
Areas z
zip codes, census blocks, tracts, places, counties, etc.
Points landmarks such as churches, schools, and other cultural features represented in TIGER as points
z
Linear Address Matching (Streets) Urban street maps Four street address numbers ranging from low to high for each side of a street segment. Left_from 101
Left_to 199
Right_from 100 0105 0107
Right_to 198
Street_name OAK
100 101 (80.731, 40.025)
Oak St.
Type ST 198 199 (80.729, 40.025)
Address Matching Major Steps Schools file ID
Address
Class
1437
123 Oak St
A
402
333 Pine Av
A
855
18 Bay Dr
B
Address Matching Major Steps Schools ID
Address
Class
1437
123 Oak St
A
402
333 Pine Av
A
855
18 Bay Dr
B
Attributes of Streets Parity
Street_
From
To
Street
Type
Side
2
98
Oak
St
R
E
5950
1
99
Oak
St
L
O
5950
100
198
Oak
St
R
E
6011
101
199
Oak
St
L
O
6011
Address Matching Major Steps schools Address
Class
1437
123 Oak St
A
402
333 Pine Av
A
855
18 Bay Dr
Oak St 100
5950 Pine Av
StoreID
B
6011
101
199 123
Attributes of Streets Parity
198
Street_
From
To
Street
Type
Side
2
98
Oak
St
R
E
5950
1
99
Oak
St
L
O
5950
100
198
Oak
St
R
E
6011
101
199
Oak
St
L
O
6011
Converting Georeferences GIS applications often require transforming data so that they line up These are standard functions in popular GIS packages
Street addresses must be converted to coordinates for mapping and analysis Using geocoding functions
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