TIGER/Line Files, 1995

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Frequently anticipated questions:


What does this data set describe?

Title: TIGER/Line Files, 1995
Abstract:
TIGER, TIGER/Line, and Census TIGER are trademarks of the Bureau of the Census. The 1995 TIGER/Line files are an extract of selected geographic and cartographic information from the Census TIGER data base. The geographic coverage for a single TIGER/Line file is a county or statistical equivalent entity, with the coverage area based on January 1, 1995 legal boundaries. A complete set of 1995 TIGER/Line files includes all counties and statistically equivalent entities i the United States, the U.S. Virgin Islands, Puerto Rico, American Samoa, Guam, the Northern Marian Islands, U.S. Minor Outlying Areas, and the Pacific Island Territories. The Census TIGER data base represents a seamless national file with no overlaps or gaps between parts. However, each county-based TIGER/Line file is designed to stand alone as an independent data set or the files can be combined to cover the whole Nation and its territories. The 1995 TIGER/Line files consist of line segments representing physical features and governmental and statistical boundaries. The files contain information distributed over a series of record types for the spatial objects of a county. There are 17 record types, including the basic data record, the shape coordinate points, and geographic codes that can be used with appropriate software to prepare maps. Other geographic information contained in the files includes attributes such as feature identifiers/census feature class codes (CFCC) used to differentiate feature types, address ranges and ZIP Codes, codes for legal and statistical entities, latitude/longitude coordinates of linear and point features, landmark point features, area landmarks, key geographic features, and area boundaries. The 1995 TIGER/Line data dictionary contains a complete list of all the fields in the 17 record types.
Supplemental_Information:
To find out more about TIGER/Line files and other Census TIGER data base derived data sets visit <http://www.census.gov/geo/www/tiger>. Note: The spatial domain element of this metadata only list the maximum and minimum bounding coordinates for the continental United States. See the TIGER/Line Files Maximum and Minimum Coordinates File for the maximum and minimum coordinates for each TIGER/Line file county or statistical equivalent.
  1. How should this data set be cited?

    U.S. Department of Commerce Bureau of the Census Geography Division, 1996, TIGER/Line Files, 1995: TIGER/Line Census Files Version (0024), U.S. Department of Commerce Bureau of the Census Geography Division, Washington, DC.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -124.848974
    East_Bounding_Coordinate: -66.885075
    North_Bounding_Coordinate: 49.384363
    South_Bounding_Coordinate: 24.395877

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Calendar_Date: 1995
    Currentness_Reference: 1995

  5. What is the general form of this data set?

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      Indirect_Spatial_Reference:
      Federal Information Processing Standards (FIPS) and feature names and addresses.
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • Node, network (570 to 56,000)
      • Entity point
      • Complete chain (790 to 83,000)
      • GT-polygon composed of chains (290 to 33,000)

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000458. Longitudes are given to the nearest 0.000458. Latitude and longitude values are specified in Decimal degrees.

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview:
    The TIGER/Line files contain data describing three major types of features/entities; Line Features - 1) Roads 2) Railroads 3) Hydrography 4) Miscellaneous transportation features and selected power lines and pipe lines 5) Political and statistical boundaries Landmark Features - 1) Point landmarks, e.g., schools and churches. 2) Area landmarks, e.g., Parks and cemeteries. 3) Key geographic locations (KGLs), e.g., apartment buildings and factories. Polygon features - 1) Geographic entity codes for areas used to tabulate the 1990 census statistical data and current geographic areas 2) Locations of area landmarks 3) Locations of KGLs The line features and polygon information form the majority of data in the TIGER/Line files. Some of the data/attributes describing the lines include coordinates, feature identifiers (names), CFCCs (used to identify the most noticeable characteristic of a feature), address ranges, and geographic entity codes. The TIGER/Line files contain point and area labels that describe landmarks features and provide locational reference. Area landmarks consist of a feature name or label and feature type assigned to a polygon or group of polygons. Landmarks may overlap or refer to the same set of polygons. The Census TIGER data base uses collections of spatial objects (points, lines, and polygons) to model or describe real-world geography. The Census Bureau uses these spatial objects to represent features such as streets, rivers, and political boundaries and assigns attributes to these features to identify and describe specific features such as the 500 block of Market Street in Philadelphia, Pennsylvania. The TIGER/Line files contain information about these spatial objects distributed over a series of record types. Users of the TIGER/Line files may need to link information from several record types to find all the attributes of interest that belong to one spatial object. Topology explains how points, lines, and areas relate to each other and is used as the foundation for organizing spatial objects in the Census TIGER data base. The Census TIGER data base uses these objects to provide a disciplined, mathematical description of the features on the earth's surface. All spatial objects are interrelated. A sequence of points define line segments, and line segments connect to define polygons. The Census TIGER data base relates information to points or 0-cells, lines or 1-cells, and polygons or 2-cells. The number preceding the cell identifies the dimensionality of the objects; for instance, a line segment has a single dimension, length. Each of these objects build on the others to form higher-level objects. The 0-cells form the end points of 1-cells. The 1-cells connect at 0-cells and form closed figures that partition space into polygons or 2-cells. The spatial objects in TIGER/Line files embody both geometry (coordinate location and shape) and topology (the relationship between points, lines objects, and polygons) and therefore belong to the "Geometry and Topology" (GT) class of objects in the SDTS. In the SDTS, nodes represent point objects (0-cells) that identify the start and end position of lines or 1-dimensional objects (1-cells) called chains. The chains in the TIGER/Line files are complete chains because they form GT-polygon boundaries and intersect other chains only at nodes. Topological chains that do not contain polygon information are network chains used to form GT-rings. Data users may choose not to use GT-polygon or geographic entity codes and consider the TIGER/Line files a source of network chain data. The TIGER/Line files contain point landmark data that are not included in the Census TIGER data base topology. Point landmarks are entity points that mark the location of points of interest and are not connected to complete chains or GT- polygons. A polygon identification code is used to link a landmark to a GT-polygon.
    Entity_and_Attribute_Detail_Citation:
    The U.S. Bureau of the Census, TIGER/Line Files, 1995 Technical Documentation. The TIGER/Line files documentation defines the terms and definitions used within the files.


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    U.S. Department of Commerce Bureau of the Census Geography Division

  3. To whom should users address questions about the data?

    U.S. Department of Commerce Bureau of the Census Geography Division Products and Services Staff
    8903 Presidential Pkwy, WP I
    Upper Marlboro, Maryland 20772
    USA

    1 301 457 1128 (voice)
    1 301 457 4710 (FAX)
    TIGER@census.gov

    Hours_of_Service: Monday through Friday 8:30 A.M. to 4:30 P.M. EST-USA


Why was the data set created?

In order for others to use the information in the Census TIGER data base in a geographic information system (GIS) or for other geographic applications, the Census Bureau releases to the public extracts of the data base in the form of TIGER/Line files. Various versions of the TIGER/Line files have been released; previous versions include the 1990 Census TIGER/Line files (version 0003), the 1992 TIGER/Line files (version 0005), and the 1994 TIGER/Line files (version 0021). The 1995 (version 0024) TIGER/Line files were originally produced to support Phase I of the Census 2000 Redistricting Data Program.


How was the data set created?

  1. From what previous works were the data drawn?

    TIGER (source 1 of 1)
    U.S. Department of Commerce Bureau of the Census Geography Division, Unpublished material, TIGER data base.

    Type_of_Source_Media: On line
    Source_Contribution:
    Selected geographic and cartographic information (line segments) from the Census TIGER data base.

  2. How were the data generated, processed, and modified?

    Date: 1996 (process 1 of 1)
    In order for others to use the information in the Census TIGER data base in a GIS or for other geographic applications, the Census Bureau releases periodic extracts of selected information from the Census TIGER data base, organized as topologically consistent networks. Software (TIGER DB routines) written by the Geography Division allows for efficient access to Census TIGER system data. TIGER/Line files are extracted from the Census TIGER data base by county or statistical equivalent area. Census TIGER data for a given county or statistical equivalent area is then distributed among 17 fixed length record ASCII files, each one containing attributes for either line, polygon, or landmark geographic data types. The Bureau of the Census has released various versions of the TIGER/Line files since 1988, with each version having more updates (feature and feature names, address ranges and ZIP Codes, coordinate updates, new record types, revised field definitions, etc.), than the previous version.

    Person who carried out this activity:

    U.S. Department of Commerce Bureau of the Census Products and Services Staff
    8903 Presidential Parkway, WP I
    Upper Marlboro, Maryland 20772
    USA

    1 301 457 1128 (voice)
    1 301 457 4710 (FAX)
    TIGER@census.gov

    Data sources used in this process:
    • TIGER data base

  3. What similar or related data should the user be aware of?


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    Accurate against Federal Information Processing Standards (FIPS), FIPS Publication 6-4, and FIPS-55 at the 100% level for the codes and base names. The remaining attribute information has been examined but has not been fully tested for accuracy.

  2. How accurate are the geographic locations?

    The information present in these files is provided for the purposes of statistical analysis and census operations only. Coordinates in the TIGER/Line files have six implied decimal places, but the positional accuracy of these coordinates is not as great as the six decimal places suggest. The positional accuracy varies with the source materials used, but generally the information is no better than the established National Map Accuracy standards for 1:100,000-scale maps from the U.S. Geological Survey (USGS); thus it is NOT suitable for high-precision measurement applications such as engineering problems, property transfers, or other uses that might require highly accurate measurements of the earth's surface. The USGS 1:100,000-scale maps meet national map accuracy standards and use coordinates defined by the North American Datum, 1983. For the contiguous 48 States, the cartographic fidelity of most of the 1995 TIGER/Line files, in areas outside the 1980 census Geographic Base File/Dual Independent Map Encoding (GBF/DIME) file coverage and selected other large metropolitan areas, compare favorably with the USGS 1:100,000-scale maps. The Census Bureau cannot specify the accuracy of features inside of what was the 1980 GBF/DIME-Files coverage or selected metropolitan areas. The Census Bureau added updates to the TIGER/Line files that enumerators annotated on map sheets prepared from the Census TIGER data base as they attempted to traverse every street feature shown on the 1990 census map sheets; the Bureau also made other corrections from updated map sheets supplied by local participants for Census Bureau programs. The locational accuracy of these updates is of unknown quality. In addition to the Federal, State, and local sources, portions of the files may contain information obtained in part from maps and other materials prepared by private companies. Despite the fact that TIGER/Line data positional accuracy is not as high as the coordinates values imply, the six-decimal place precision is useful when producing maps. The precision allows features that are next to each other on the ground to be placed in the correct position, on the map, relative to each other, without overlap.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    Data completeness of the TIGER/Line files reflects the contents of the Census TIGER data base at the time the TIGER/Line files (1995 version) were created.

  5. How consistent are the relationships among the observations, including topology?

    The feature network of lines (as represented by Record Types 1 and 2) is complete for census purposes. Spatial objects in TIGER/Line belong to the "Geometry and Topology"(GT) class of objects in the "Spatial Data Transfer Standard" (SDTS) FIPS Publication 173 and are topologically valid. Node/geometry and topology (GT)-polygon/chain relationships are collected or generated to satisfy topological edit requirements. These requirements include: * Complete chains must begin and end at nodes. * Complete chains must connect to each other at nodes. * Complete chains do not extend through nodes. * Left and right GT-polygons are defined for each complete chain element and are consistent throughout the extract process. * The chains representing the limits of the file are free of gaps. The Census Bureau performed automated tests to ensure logical consistency and limits of files. All polygons are tested for closure. Some polygons in the TIGER/Line files may be so small that the polygon internal point has been manually placed on a node that defines the polygon perimeter. These small polygons have been detected, and corrections will be incorporated in the Census TIGER data base in the future. The Census Bureau uses its internally developed Geographic Update System to enhance and modify spatial and attribute data in the Census TIGER data base. Standard geographic codes, such as FIPS codes for states, counties, municipalities, and places, are used when encoding spatial entities. The Census Bureau performed spatial data tests for logical consistency of the codes during the compilation of the original Census TIGER data base files. Most of the codes themselves were provided to the Census Bureau by the USGS, the agency responsible for maintaining FIPS 55. Feature attribute information has been examined but has not been fully tested for consistency.


How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None
Use_Constraints:
None. Acknowledgment of the U.S. Bureau of the Census would be appreciated for products derived from these files. TIGER, TIGER/Line, and Census TIGER are trademarks of the Bureau of the Census.

  1. Who distributes the data set? (Distributor 1 of 1)

    U.S. Department of Commerce Bureau of the Census Geography Division Products and Services Staff
    8903 Presidential Parkway, WP I
    Upper Marlboro, Maryland 20772
    USA

    1 301 457 1128 (voice)
    1 301 457 4710 (FAX)
    TIGER@census.gov

  2. What's the catalog number I need to order this data set?

    1995 TIGER/Line Files

  3. What legal disclaimers am I supposed to read?

    No warranty, expressed or implied is made and no liability is assumed by the U.S. Government in general or the Bureau of the Census in specific as to the positional or attribute accuracy of the data. The act of distribution shall not constitute any such warranty and no responsibility is assumed by the U.S. Government in the use of these files.

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    The 1995 TIGER/Line files contain geographic data only and do not include display or mapping software or statistical data. A list of vendors who have developed software capable of processing TIGER/Line files can be obtained over the Internet by selecting TIGER under Subjects A-Z on the Census Bureau's home page (www.census.gov).


Who wrote the metadata?

Dates:
Last modified: Dec-1996
Last Reviewed: 30-Jan-1997
Metadata author:
Lornell A. Parks
U.S. Department of Commerce Bureau of the Census Geography Division Geospatial Research and Standards Staff
8903 Presidential Parkway, WP I
Upper Marlboro, Maryland 20772
USA

1 301 457 1056 (voice)
1 301 457 4710 (FAX)
lparks@census.gov

Metadata standard:
Federal Geographic Data Committee "Content Standards for Digital Geospatial Metadata" (FGDC-STD-001-1998)


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