DATABASE NAME

     URBAN:  1:100,000 base-map scale Federally Adjusted Urban
     Boundaries

DATABASE DESCRIPTION

     1:100,000 base-map scale federally adjusted urban boundaries
     for urban areas > 50,000 population.

ORIGINATING AGENCY

     Federal Highway Administration, Office of Environment and
     Planning

AGENCY RESPONSIBLE FOR MAINTAINING DATA

     Federal Highway Administration, Office of Environment and
     Planning

CONTACT

     National Transportation Atlas Databases
     Bureau of Transportation Statistics
     U.S. Department of Transportation
     Washington, DC  20590
     (202) 366-DATA
     Internet:  info@bts.gov

SOURCE

     1990 1:100,000 Census TIGER/Line records integrated with the
     State digital sources supplemented by editing performed by
     the University of Tennessee for the Federal Highway
     Administration

ACCURACY

     80 m (165 mi) root-mean square positional accuracy of
     TIGER/Line boundaries

TYPE OF GIS DATABASE

     Area database with polygons and links

FILES/SIZE/NUMBER OF RECORDS

     Two ASCII files

     1)   urban.ply      polygon file contains area attributes
     2)   urban.lin      link file contains link attributes,
                         locations, and shapes

     Approximate size of files:    9,293,000 bytes
     Approximate number of areas:  530
     Approximate number of links:  6600

FILE STRUCTURE

     The files are ASCII - fixed format.  Character fields are
     not enclosed in quotation marks.

     The Polygon File

     The Polygon Record File contains a single 99 byte record for
     each polygon representing a large urban area, delimited by a
     CR/LF.  Each field in the Polygon File is described below:

     RECTYPE
          Data Type:          Character
          Width:              1
          Starting Position:  1
          Domain:             'P'
          Description:        Identifies Polygon Records

     VERSION
          Data Type:          short int
          Width:              2
          Starting Position:  2
          Domain:             positive integers
          Description:        This field describes the release
                              version of the database.  The
                              VERSION code consists of a leading
                              Version Number and a trailing
                              Revision Number; thus, 10 denotes
                              Version 1 Revision 0.  Similarly, a
                              VERSION value of 21 would denote
                              Version 2 Revision 1.

     SOURCE
          Data Type:          Character
          Width:              1
          Starting Position:  4
          Domain:             'U'
          Description:        The SOURCE flag is used to describe
                              the original source of the
                              attribute data in the Polygon
                              Record.  The following flags will
                              be present:
                                   'U'  University of Tennessee
                                        source

     RECID
          Data Type:          long int
          Width:              8
          Starting Position:  5
          Domain:             positive integers
          Description:        The RECID is a unique numeric
                              identifier associated with each
                              Polygon Record.  RECIDs are
                              permanent and are not reused.

     SQMILES
          Data Type:          float
          Width:              7
          Decimal Places:     2
          Starting Position:  13
          Domain:             positive real numbers
          Description:        The SQMILES field is an
                              approximation of the area of the
                              polygon in square miles

     SQKM
          Data Type:          float
          Width:              7
          Decimal Places:     2
          Starting Position:  20
          Domain:             positive real numbers
          Description:        The SQKM field is an approximation
                              of the area of the polygon in
                              square kilometers

     NAME
          Data Type:          Character string
          Width:              40
          Starting Position:  27
          Domain:             printable ASCII characters
          Description:        The NAME filed consists of a
                              descriptive name for the polygon
                              feature.  The description is right
                              justified in the field.  Only
                              capital letters are used.  The NAME
                              field may contain embedded blanks.

     URBCODE
          Data Type:          short int
          Width:              3
          Starting Position:  67
          Domain:             positive integers
          Description:        The URBCODE provides the 3 digit
                              HPMS Urbanized Area Code for the
                              adjusted urbanized area.

     CENCODE
          Data Type:          short int
          Width:              4
          Starting Position:  70
          Domain:             positive integers
          Description:        The CENCODE provides the equivalent
                              4 digit CENSUS assigned Urbanized
                              Area Code for the adjusted
                              urbanized area.

     STFIPS
          Data Type:          short int
          Width:              2
          Starting Position:  74
          Domain:             positive integers
          Description:        The FIPS code for the state within
                              which the polygon is contained.

     CENTER_X
          Data Type:          float
          Width:              12
          Decimal Places:     6
          Starting Position:  76
          Domain:             real numbers
          Description:        The longitude location in decimal
                              degrees for the calculated centroid
                              of the polygon.

     CENTER_Y
          Data Type:          float
          Width:              12
          Decimal Places:     6
          Starting Position:  88
          Domain:             real numbers
          Description:        The latitude location in decimal
                              degrees for the calculated centroid
                              of the polygon.

     The Link File

     The Line Record File contains a single 41 byte header record
     for each line in the large urban database, followed by a
     list of shape points stored in multiple 96 byte records. 
     The maximum number of shape points for any line is set to
     500.  All records are delimited with a CR/LF.  Line Records
     are either boundaries or closure lines which are used to
     artificially delineate polygon boundaries when no physical
     boundary exists.  For example state borders are modeled as
     closure lines.  Each Line Record contains the following
     structure.

               COLUMN         TYPE      WIDTH

               RECTYPE        char           1
               VERSION        short int      2
               SOURCE         char           1
               RECID          long int       8
               FEATURE        char           1
               STFIPSL        short int      2
               STFIPSR        short int      2
               POLYL          long int       8
               POLYR          long int       8
               NPOINTS        short int      8

     The line record is followed by NPOINTS coordinates tuples
     stored in FORTRAN(8F12.6) format.  Each tuple is stored as
     X,Y (longitude, latitude) in decimal degrees.  Each field in
     the Line File is described more fully below.

     RECTYPE
          Data Type:          Character
          Width:              1
          Starting Position:  1
          Domain:             'L'
          Description:        Identifies Line Records

     VERSION
          Data Type:          short int
          Width:              2
          Starting Position:  2
          Domain:             positive integers
          Description:        This field describes the release
                              version of the database.  The
                              VERSION code consists of a leading
                              Version Number and a trailing
                              Revision Number; thus, 10 denotes
                              Version 1 Revision 0.  Similarly, a
                              VERSION value of 21 would denote
                              Version 2 Revision 1.

     SOURCE
          Data Type:          Character
          Width:              1
          Starting Position:  4
          Domain:             'N', 'T', 'U'
          Description:        The SOURCE flag is used to describe
                              the original source of the
                              topographic data in the Line
                              Record.  The following flags will
                              be present:
                                   'N'  National Oceanic and
                                        Atmospheric
                                        Administration (NOAA)
                                        (1:250,000)
                                   'T'  Census TIGER/Line Records
                                        (1:100,000)
                                   'U'  University of Tennessee
                                        source

     RECID
          Data Type:          long int
          Width:              8
          Starting Position:  5
          Domain:             positive integers
          Description:        The RECID is a unique numeric
                              identifier associated with each
                              Polygon Record.  RECIDs are
                              permanent are not reused.

     FEATURE
          Data Type:          Character
          Width:              1
          Starting Position:  13
          Domain:             'B', 'C'
          Description:        The FEATURE field describes the
                              feature type of the line.  The
                              following FEATURE codes are
                              present:
                                   'B'  Boundary Line
                                   'C'  Closure line

     STFIPSL
          Data Type:          short int
          Width:              2
          Starting Position:  14
          Domain:             positive integers
          Description:        The FIPS code for the state, to the
                              left, within which the polygon is
                              contained.

     STFIPSR
          Data Type:          short int
          Width:              2
          Starting Position:  16
          Domain:             positive integers
          Description:        The FIPS code for the state, to the
                              right, within which the polygon is
                              contained.

     POLYL
          Data Type:          long int
          Width:              8
          Starting Position:  18
          Domain:             positive integers
          Description:        RECID for the polygon to the left
                              side of the line.

     POLYR
          Data Type:          long int
          Width:              8
          Starting Position:  26
          Domain:             positive integers
          Description:        RECID for the polygon to the right
                              side of the line.

     NPOINTS
          Data Type:          short int
          Width:              8
          Starting Position:  34
          Domain:             positive integers
          Description:        The number of shape points to
                              follow in the Line Record.

DISCUSSION

     Introduction

     This document describes the format and structure of the
     Adjusted Urbanized Area (AUB) Borders geographic database. 
     The AUB database is a geographic database consisting of
     Adjusted Urbanized Areas in the United States and selected
     territories for 1993; wherein, the Adjusted Urbanized Areas
     contain state-portions of adjusted CENSUS urban boundaries
     for 399 urban areas with a 1990 CENSUS population greater
     than 50,000 people.  This database was compiled by members
     of the Geographic Information Systems Group at the
     University of Tennessee, Pellissippi Research Institute in
     Knoxville, Tennessee for the Federal Highway Administration,
     Office of Environment and Planning, HEP-11.  It was
     developed as a mapping database for use within Geographic
     Information Systems and other computer-aided mapping
     software.

     Overview

     The Adjusted Urbanized Area database contains polygon and
     line records for the 48 contiguous states, Washington DC,
     Alaska, Hawaii, and Puerto Rico.  It is distributed in two
     files: a Polygon Record File and a Line Record File.  Each
     file contains fixed length ASCII records and is organized
     such that each state will build as a complete set of
     polygons.  Closure is achieved by adding lines (closure
     lines) to artificially bound polygons where no physical
     boundary exists such as at a state boundary where an urban
     area straddles more that one state.  The database is
     constructed using a DIME-like file structure.  The DIME
     structure encodes polygon topology onto line segments by
     defining left and right side polygon attributes and
     attributing each line in the database with unique direction. 
     The DIME structure enables polygons sharing common
     boundaries to be modeled simply, without redundant lines
     being present in the database.  Associated with each polygon
     is a centroid which references a polygons attribute
     information.  A single infinitely large unbounded polygon,
     termed the external or universal polygon, is defined to
     ensure complete closure of all polygons in the database. 
     Every polygon in the database lies within the universe
     polygon.

     Each feature in the database has a unique permanent record
     identifier, and each record contains a descriptive section
     which references the version and source of the original
     data.  The external polygon is always reference with a
     polygon ID of 0(zero).  Note that the universe polygon has
     no polygon record or centroid associated with it.

     Data Sources

     The Adjusted Urbanized Area database has been developed by
     combining a variety of digital data and digitized maps,
     primarily from State DOTs.  Where possible, the boundary
     information was assimilated directly from State digital
     sources and adjusted to coincide with political boundaries
     from CENSUS TIGER lines.  Where States submitted boundary
     lines on map sheets, the map sheets were digitized and the
     results edited into polygons and appended into the national
     dataset.

     Attribute information for the Adjusted Urbanized Area
     polygon records was obtained from the Highway Performance
     Monitoring System (HPMS) for 1991.  Area attributes for the
     polygons were calculated using Arc/Info V6.1.1 GIS Software
     (ESRI 1991).  Other map features and attributes such as
     closure lines and FIPS codes were added by members of the
     development staff.
