help DLGARC

DLGARC <STANDARD | OPTIONAL> <in_dlg_file> <out_cover> {out_point_cover}
       {NOFIRST | ALL | ATTRIBUTED} {x_shift} {y_shift} {category}
 
converts a Digital Line Graph (DLG) file in either Standard or Optional format
into ARC/INFO coverages.
 
arguments
 
<STANDARD | OPTIONAL> - specifies whether the DLG file to be read is
in Standard or Optional format.
 
STANDARD - distribution format (144 bytes per record) intended to minimize
storage requirements.
 
OPTIONAL - optional distribution format (80 bytes per record) containing
linkages for line, node and area features usually in meters in the UTM
coordinate system.
 
<in_dlg_file> - the name of the DLG file to be read.
 
<out_cover> - the name of the coverage to be created from the DLG data.  If
<in_dlg_file> contains data produced by USGS, <out_cover> will usually contain
line, polygon and node features created from nondegenerate Line (L) records,
Area (A) records and Node (N) records.  An <out_cover>.NAT for node features
will be created.  This is the only feature attribute table that is created by
DLGARC.  An INFO data file named <out_cover>.ACODE will be created that
contains the major/minor pair values for all Line (L) records.  Similarly, an
INFO data file named <out_cover>.PCODE will store the major/minor codes for
Area (A) records.
 
{out_point_cover} - the name of an optional point coverage to be created from
degenerate Line (L) records in the DLG.  In a DLG, points are stored as zero-
length arcs (i.e., degenerate lines).  These are optionally converted to points
by specifying a {out_point_cover}.  An INFO data file named
{out_point_cover}.XCODE will be created which contains all major and minor code
pair values for degenerate Line (L) records.  No coverage will be created from
degenerate line records unless a {out_point_cover} is specified.
 
{NOFIRST | ALL | ATTRIBUTED} - determines how the Area (A) records are written
to the <out_cover>.
NOFIRST - the first Area record is ignored.  Labels are written for all other
Area records and the corresponding major/minor codes are written to the
<out_cover>.PCODE file.  This is the default option.
 
ALL - all Area records are converted to <out_cover> label points and the major
and minor codes for all the Area (A) records in the <out_cover>.PCODE file.
Usually the label point for the first Area record is in the outside polygon.
 
ATTRIBUTED - the label location in the DLG file is used only for those Area
records that carry major/minor codes.  The remaining label locations are
calculated to fit inside the polygons they represent.  For some DLG categories,
only Area records with attributes have valid label locations.  The first Area
(A) record is not included.
 
{x_shift} - a constant value to be added to all x-coordinates during DLG
conversion.  The default {x_shift} value is 0.
 
{y_shift} - a constant value to be added to all y-coordinates during DLG
conversion.  The default {y_shift} value is 0.
 
{category} - the optional name of a specific DLG category to be converted from
the DLG file.  Only the specified {category} will be converted if one is given.
Otherwise, only the first category in the DLG will be written to the output
coverages:  <out_cover>, {point_cover}.  A DLG category is equivalent to a
layer.  Usually, only one category is included in a DLG file.  However, some
DLGs contain more than one category.  Categories are listed in DLG Header
records.  Use of {category} enables you to create a set of coverages for other
layers or categories contained in the DLG.
 
notes
 
Topology data contained in the DLG file are ignored.  The ARC commands
CLEAN and BUILD can be used to create topology after DLG files are converted
into ARC/INFO coverages.
 
The coordinate precision of the output coverage is determined by the current
creation rule as set by the PRECISION command.  If the precision
not yet been established during the current ARC/INFO session,
then the creation rule will be SINGLE.  This means that DLGARC will create
an output coverage in single precision.  (Coordinate values in DLG files have a
format definition of F12.2.)
 
Feature numbers in the DLG Area (A) records become label point User-IDs for
polygons; feature numbers in Line (L) records become User-IDs for arcs in the
<out_cover>.  The same User-IDs are written to the INFO data files
<out_cover>.ACODE, <out_cover>.PCODE.
 
CODE files <out_cover>.ACODE and <out_cover>.PCODE hold Line attribute codes
and polygon attribute codes.
 
The DLG feature numbers for Node (N) records become User-IDs for nodes in
<out_cover>.  There is no corresponding CODE file for node attributes.  The
User-IDs and attribute codes for Node (N) records are stored directly in the
<out_cover>.NAT feature attribute table.
 
For {out_point_cover}, the DLG feature numbers in degenerate (zero-length) Line
(L) records become User-IDs for points in {out_point_cover}.  An
{out_point_cover}.XCODE is created to hold degenerate Line (L) attribute codes.
 
CODE files for a particular feature class are only created if feature
attributes are found in the DLG.
 
The items for each CODE file created in INFO by DLGARC consist of the
following:
 
COL ITEM NAME        WDTH OPUT TYP N.DEC
 1  cover-ID            4    6  B    -
 5  MAJOR1              6    6  I    -
 9  MINOR1              6    6  I    -
13  MAJOR2              6    6  I    -
17  MINOR2              6    6  I    -
 .    .                 .    .  .    .
 .    .                 .    .  .    .
 .    .                 .    .  .    .
 .  MAJORn              6    6  I    -
Continue? |
 .  MINORn              6    6  I    -
 
Cover-ID is each feature's unique identifier.  MAJOR1 is the first major
feature code in the DLG; MINOR1 is the first minor code.  There are as many
major/minor pairs in the table as the maximum number of pairs for that feature
class in the DLG.  If no value appears for a particular code, it will be set to
-99999 in the INFO data file to signify 'No data'.
 
 DLGARC writes the projection parameters stored in the DLG file to a projection
definition file (PRJ) stored in the <out_cover> subdirectory.
 
This example shows the parameters stored for the <out_cover>.
 
    PROJECTION UTM
    UNITS METERS
    ZONE 16
    YSHIFT 3000000
    PARAMETERS
 
Any values specified for {x_shift} and {y_shift} are also used to create XSHIFT
and YSHIFT records in the PRJ file.  Users may find it necessary to specify a
negative shift when creating the coverages and a positive shift when writing
the coverages back out to a DLG file in order to preserve accuracy of the
coordinates.  Unless specified as arguments to ARCDLG, the XSHIFT YSHIFT
parameters are read from the PRJ file if it exists.  The PRJ file is also used
by ARC PROJECT and ARCPLOT MAPPROJECTION commands.
 
The DLG header records may also contain parameters of a transformation which
are used to convert the internal file coordinates to the ground coordinate
system.  DLGARC will automatically apply any transformation parameters found in
the header records to the feature coordinates and control points (in addition
to any specified shift).
 
The header records in the DLG file provide information used to determine the
TIC locations of the output coverages.
 
If the fields used to store control point information are blank, DLGARC will
generate TICS for the output coverages.
 
DLG files usually provide four control points representing the four corners of
the map area in the same map coordinate system used to store geographic
features.  Any transformation or x,y shift applied to the feature coordinates
will apply to the control points as well.
 
The output coverage from DLGARC may require editing before polygons or lines
can be built and feature attribute tables can be created.  For example, checks
should be made on the output coverage to ensure that label points occur within
their polygons, arcs match at nodes, polygons close, arcs do not cross, and so
on.
 
The ARCDLG command is used to create an Optional format DLG file from a
coverage.  Refer to the ARCDLG command reference for details.
 
