NAME
v.in.dlg2 - Converts an ASCII or binary USGS DLG-3
(bdlg) file to a binary GRASS vector (dig) file.
(GRASS Vector Data Import Program)
SYNOPSIS
v.in.dlg2
v.in.dlg2 help
v.in.dlg2 [-bl] input=name output=name
DESCRIPTION
This program converts an ASCII or binary USGS DLG-3
(dlg.old or bdlg.old) file
into a binary GRASS vector (dig) file.
v.in.dlg2 also creates a dig_att file
containing the label information 'stripped' from the DLG-3
file. However, the user must run
v.support (or
v.import option 4)
on the output file created by v.in.dlg2
to create a dig_plus file containing the file
topology, before using the output file in
v.digit.
The user can avoid this two-step process by converting the
ASCII or binary DLG-3 file to binary GRASS vector format
using option 1 or 2 of the GRASS program
v.import.
OPTIONS
Flags:
- -b
- Input is a binary DLG-3 file (default is ASCII).
- -l
- Give precedence to line information (default is area).
Parameters:
- input=name
- Name of USGS DLG-3 Optional format input file.
- output=name
- Name to be assigned to the binary GRASS vector files created.
If the user simply types v.in.dlg2 without specifying parameter
values on the command line, the program will prompt the user to enter these.
NOTES
Area vs Line Precedence:
Some machine-processed DLG-3 files do not make the
distinction between line edges and area edges. For
example, in a roads map, where the desired information is
line edge data, a downtown block surrounded by roads may be
processed as an area. Because of this, the user is asked
to choose whether to give precedence to areas or lines. If
precedence is given to lines, the user should be aware that
any lines that bound unlabeled areas in the DLG-3 file will
be stored as line data. Any unlabeled areas would
therefore be lost (this is only a concern when areas are
unlabeled; labeled area information will be retained). If
precedence is given to areas, lines will be stored as
boundaries to areas that are unlabeled.
Building support files with
v.support:
When you run
v.support
you will have the option of snapping the nodes in your
vector file that fall within a certain threshold of one
another. WARNING: the default threshold is calculated
using the scale of the original DLG-3 file. If the
threshold is too high, excessive snapping may occur,
destroying the file!! With
v.support,
the user has the option of snapping or not snapping nodes,
and further, of setting a particular snapping threshold.
SEE ALSO
v.digit,
v.import,
v.support
AUTHOR
Michael Higgins,
U.S.Army Construction Engineering
Research Laboratory
Dave Gerdes, U.S.Army Construction Engineering
Research Laboratory