227
How Do You Model a Network for Geospatial Technology?
of road network data in a format usable by geospatial technology software.
The data is provided in the TIGER/Line files. TIGER stands for Topologically
Integrated Geographic Encoding Referencing and the files delineate different
boundaries throughout the United States (such as congressional districts), in
addition to containing road-network data. (See Hands-on Application 8.1: TIGER Files Online for more information.)
Each record in a TIGER/Line file represents a segment of a road network,
and thus each segment (record) can have multiple attributes (fields) assigned
to it. Figure 8.3 on page 228 again shows a TIGER/Line file of Virginia Beach
and a portion of the attribute table of those selected segments that make up
Virginia Beach Boulevard. Note how many attributes there are (information
that gets encoded into each road segment, and the entire Virginia Beach TIGER/Line file is made up of over 19,000 segments). The TIGER/Line file contains the following standard attributes (among others):
a FEDIRP: This is the prefix direction of the road (N. Smith St. or W.
Broad Ave.).
a FENAME: This is the name of the road (N. Smith St. or W. Broad Ave.).
a FETYPE: This is the type of road (N. Smith St. or W. Broad Ave.).
a FEDIRS: This is the suffix direction of the road (Cherry Lane S. or Canal
Street E.).
a CFCC: This is the Census Feature Class Code, a standardized encoding
used to separate different kinds of roads (such as residential street, highways, or interstates).
TIGER files are made freely available from the
Census Bureau via the Web. Open your Web browser and go to http://www.census.gov/geo/www/
tiger—this is the part of the U.S. Census Bureau’s
Website for downloading TIGER/Line files. There’s
also full documentation of TIGER files available in
PDF format on the Website. Files for U.S. counties
can be downloaded in shapefile format (see Chapter
5 for more info about shapefiles) to be used in GIS
products such as ArcGIS or ArcExplorer Java Edition
for Educators. You can also download several other
types of TIGER files besides road-network data, including census block information, hydrography, landmarks, and American Indian reference data—check
to see what types of datasets are available for
download.
Esri also makes TIGER 2000 data freely
available—this data has already been separated into
its various components (such as roads, railroads,
etc.) for download so that each layer can be downloaded as its own shapefile. Open your Web browser
and go to http://arcdata.esri.com/data/tiger2000/
tiger_download.cfm. All data is downloaded in a
zipped shapefile format (same as the U.S. Census
Bureau’s Website) for use in ArcGIS or AEJEE. Select
your county to see what TIGER data is available for
you to use. This chapter’s lab uses a TIGER dataset
downloaded from the Esri Website.
Hands-on Application 8.1
TIGER Files Online
TIGER/Line a file
produced by the U.S.
Census Bureau that
contains (among other
items) the line segments
that correspond with
roads across the United
States.
How Do You Model a Network for Geospatial Technology?
of road network data in a format usable by geospatial technology software.
The data is provided in the TIGER/Line files. TIGER stands for Topologically
Integrated Geographic Encoding Referencing and the files delineate different
boundaries throughout the United States (such as congressional districts), in
addition to containing road-network data. (See Hands-on Application 8.1: TIGER Files Online for more information.)
Each record in a TIGER/Line file represents a segment of a road network,
and thus each segment (record) can have multiple attributes (fields) assigned
to it. Figure 8.3 on page 228 again shows a TIGER/Line file of Virginia Beach
and a portion of the attribute table of those selected segments that make up
Virginia Beach Boulevard. Note how many attributes there are (information
that gets encoded into each road segment, and the entire Virginia Beach TIGER/Line file is made up of over 19,000 segments). The TIGER/Line file contains the following standard attributes (among others):
a FEDIRP: This is the prefix direction of the road (N. Smith St. or W.
Broad Ave.).
a FENAME: This is the name of the road (N. Smith St. or W. Broad Ave.).
a FETYPE: This is the type of road (N. Smith St. or W. Broad Ave.).
a FEDIRS: This is the suffix direction of the road (Cherry Lane S. or Canal
Street E.).
a CFCC: This is the Census Feature Class Code, a standardized encoding
used to separate different kinds of roads (such as residential street, highways, or interstates).
TIGER files are made freely available from the
Census Bureau via the Web. Open your Web browser and go to http://www.census.gov/geo/www/
tiger—this is the part of the U.S. Census Bureau’s
Website for downloading TIGER/Line files. There’s
also full documentation of TIGER files available in
PDF format on the Website. Files for U.S. counties
can be downloaded in shapefile format (see Chapter
5 for more info about shapefiles) to be used in GIS
products such as ArcGIS or ArcExplorer Java Edition
for Educators. You can also download several other
types of TIGER files besides road-network data, including census block information, hydrography, landmarks, and American Indian reference data—check
to see what types of datasets are available for
download.
Esri also makes TIGER 2000 data freely
available—this data has already been separated into
its various components (such as roads, railroads,
etc.) for download so that each layer can be downloaded as its own shapefile. Open your Web browser
and go to http://arcdata.esri.com/data/tiger2000/
tiger_download.cfm. All data is downloaded in a
zipped shapefile format (same as the U.S. Census
Bureau’s Website) for use in ArcGIS or AEJEE. Select
your county to see what TIGER data is available for
you to use. This chapter’s lab uses a TIGER dataset
downloaded from the Esri Website.
Hands-on Application 8.1
TIGER Files Online
TIGER/Line a file
produced by the U.S.
Census Bureau that
contains (among other
items) the line segments
that correspond with
roads across the United
States.