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<html><head><title>U.S. Census TIGER/Line</title></head><body bgcolor="#ffffff"><h1>U.S. Census TIGER/Line</h1>TIGER/Line file sets are support for read access.  <p>TIGER/Line files are a digital database of geographic features, such as roads,railroads, rivers, lakes, political boundaries, census statistical boundaries,etc. covering the entire United States. The data base contains information about these features such as their location in latitude and longitude, the name, the type of feature, address ranges for most streets, the geographic relationship to other features, and other related information. They are the public product created from the Census Bureau's TIGER (Topologically Integrated Geographic Encoding and Referencing) data base of geographic information. TIGER was developed at the Census Bureau to support the mapping and related geographic activities required by the decennial census and sample survey programs. <p>Note that the TIGER/Line product does not include census demographicstatistics.  Those are sold by the Census Bureau in a separate format(not directly supported by FME), but those statistics do relate back tocensus blocks in TIGER/Line files.<p>To open a TIGER/Line dataset, select the directory containing one or moresets of data files.   The regions are counties, or county equivelents.   Eachcounty consists of a series of files with a common basename, and differentextentions.  For instance, county 1 in state 26 (Michigan) consists ofthe following file set in Tiger98. <p><pre>TGR26001.RT1TGR26001.RT2TGR26001.RT3TGR26001.RT4TGR26001.RT5TGR26001.RT6TGR26001.RT7TGR26001.RT8TGR26001.RT9TGR26001.RTATGR26001.RTCTGR26001.RTHTGR26001.RTITGR26001.RTPTGR26001.RTRTGR26001.RTSTGR26001.RTZ</pre>The TIGER/Line coordinate system is hardcoded to NAD83 lat/long degrees. This should be appropriate for all recent years of TIGER/Line production.<P>There is no update or creation support in the TIGER/Line driver.<p>The reader was implemented for TIGER/Line 1998 files, but some effort hasgone into ensuring compatibility with 1992, 1995, 1997, 1999, 2000, 2002, 2003and 2004 TIGER/Line products as well.  The 2005 products have also beenreported to work fine.  It is believe that any TIGER/Line product from the 1990's should work with the reader, with the possible loss of some version specific information.<p><h3>Feature Representation</h3>With a few exceptions, a feature is created for each record of aTIGER/Line data file.  Each file (ie. .RT1, .RTA) is translated to anappropriate OGR feature type, with attribute names matching those in theTIGER/Line product manual.<p>The TIGER/Line RT (record type), and VERSION attributes are generallydiscarded, but the MODULE attribute is added to each feature.  TheMODULE attribute contains the basename (eg. TGR26001) of the countymodule from which the feature originated.  For some keys (such as LAND,POLYID, and CENID) this MODULE attribute is needed to make the key uniquewhen the dataset (directory) consists of more than one county of data. <p>Following is a list of feature types, and their relationship to the TIGER/Line product.<p><h4>CompleteChain</h4>A CompleteChain is a polyline with an associated TLID (TIGER/Line ID). The CompleteChain features are established from a type 1 record(Complete Chain Basic Data Record), and if available it's associated type 3 record (Complete Chain Geographic Entity Codes).   As well, anytype 2 records (Complete Chain Shape Coordinates) available are used to fill in intermediate shape points on the arc.  The TLID is the primarykey, and is unique within the entire national TIGER/Line coverage.<p>These features always have a line geometry.<p><h4>AltName</h4>These features are derived from the type 4 record (Index to AlternateFeature Identifiers), and relate a TLID to 1 to 4 alternate feature namenumbers (the FEAT attribute) which are kept separately as FeatureIds features.The standard reader pipeline attaches the names from the FeatureIdsfeatures as array attributes ALT_FEDIRS{}, ALT_FEDIRP{}, ALT_FENAME{} andALT_FETYPE{}.  The ALT_FENAME{} is a list of feature names associated withthe TLID on the AltName feature. <p>Note that zero, one or more AltName records may exist for a given TLID, andeach AltName record can contain between one and four alternate names. Because it is still very difficult to utilize AltName features to relatealtername names to CompleteChains, it is anticipated that the standardreader pipeline for TIGER/Line files will be upgraded in the future, resultingin a simplification of alternate names. <P>These features have no associated geometry.<p><h4>FeatureIds</h4>These features are derived from type 5 (Complete Chain Feature Identifiers)records.  Each feature contains a feature name (FENAME), and it's associated feature id code (FEAT).  The FEAT attribute is the primary key, and isunique within the county module.  FeatureIds have a one to many relationship with AltName features, and KeyFeatures features.<p>These features have no associated geometry.<p><h4>ZipCodes</h4>These features are derived from type 6 (Additional Address Range and ZIP Code Data) records.  These features are intended to augment theZIP Code information kept directly on CompleteChain features, and thereis a many to one relationship between ZipCodes features and CompleteChainfeatures.<p>These features have no associated geometry.<p><h4>Landmarks</h4>These features are derived from type 7 (Landmark Features) records.  Theyrelate to point, or area landmarks.  For area landmarks there is a one toone relationship with an AreaLandmark record.  The LAND attribute isthe primary key, and is unique within the county module.<p>These features may have an associated point geometry.  Landmarks associatedwith polygons will not have the polygon geometry attached.  It would needto be collected (via the AreaLandmark feature) from a Polygon feature.<p><h4>AreaLandmarks</h4>These features are derived from type 8 (Polygons Linked to Area Landmarks)records.  Each associates a Landmark feature (attribute LAND) with a Polygon feature (attribute POLYID).  This feature has a many to many relationship with Polygon features.<p>These features have no associated geometry.<p><h4>KeyFeatures</h4>These features are derived from type 9 (Polygon Geographic Entity Codes) records.  They may be associated with a FeatureIds feature (via the FEATattribute), and a Polygon feature (via the POLYID attribute).  <p>These features have no associated geometry.<p><h4>Polygon</h4>These features are derived from type A (Polygon Geographic Entity Codes)records and if available the related type S (Polygon Additional GeographicEntity Codes) records.  The POLYID attribute is the primary key, uniquelyidentifying a polygon within a county module. <p>These features do not have any geometry associated with them as read bythe OGR TIGER driver.  It needs to be externally related using thePolyChainLink.  The gdal/pymod/samples/tigerpoly.py script may be usedto read a TIGER dataset and extract the polygon layer <b>with geometry</b>as a shapefile. <h4>EntityNames</h4>These features are derived from type C (Geographic Entity Names) records. <p>These features have no associated geometry.<p><h4>IDHistory</h4>These features are derived from type H (TIGER/Line ID History) records.They can be used to trace the splitting, merging, creation and deletionof CompleteChain features. <p>These features have no associated geometry.<p><h4>PolyChainLink</h4>These features are derived from type I (Link Between Complete Chains andPolygons) records.  They are normally all consumed by the standard readerpipeline while attaching CompleteChain geometries to Polygon features toestablish their polygon geometries.  PolyChainLink features have a many toone relationship with Polygon features, and a one to one relationship withCompleteChain features. <p>These features have no associated geometry.<p><h4>PIP</h4>These features are derived from type P (Polygon Internal Point) records. They relate to a Polygon feature via the POLYID attribute, and can be usedto establish an internal point for Polygon features.<p>These features have a point geometry.<p><h4>ZipPlus4</h4>These features are derived from type Z (ZIP+4 Codes) records.  ZipPlus4 features have a many to one relationship with CompleteChain features.<p>These features have no associated geometry.<p><h3>See Also</h3><ul><li> <a href="http://www.census.gov/geo/www/tiger/">http://www.census.gov/geo/www/tiger/</a>: More information on the TIGER/Line file format, and data product can be found on this U.S. Census web page.<p.</ul></body></html>
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