NAME
v.trim - Trims small spurs, and removes excessive nodes
from a binary GRASS vector (dig) file.
(GRASS Raster Program)
SYNOPSIS
v.trim
v.trim help
v.trim input=name
output=name [trim=value]
DESCRIPTION
v.trim scans the user-specified GRASS vector
input file and removes from it all lines having a
length less than a user-specified trimming factor. Excess
nodes (those unnecessary to a line's definition) between
line junctions are also removed. The resulting vector
output is sent to a user-named output file; the
original vector input file is not modified by
v.trim.
The trimming factor parameter (trim=value)
gives the user control over the size of small spurs or
"dangling lines" to be removed. The trimming factor is
expressed in the same units (map coordinates) as the vector
(dig) data within the user's current GRASS data
base LOCATION (e.g.: in meters for UTM locations; in pixels
or cells for locations in an x,y coordinate system; etc.).
OPTIONS
The user can run this program either non-interactively or
interactively. The program will be run non-interactively
if the user specifies program arguments on the command
line, using the form:
-
v.trim input=name
output=name [trim=value]
If vector map input and output names are
given on the command line, any other parameter values left
unspecified on the command line will be set to their
default values (see below). Alternately, the user can
simply type v.trim on the command line, without
program arguments. In this case, the user will be prompted
for needed parameter values using the standard GRASS
parser interface.
Parameters:
- input=name
- Name of an existing vector map layer in the user's
current mapset search path containing lines to be
"trimmed".
- output=name
- Name of a new vector file to contained the "trimmed"
output.
- trim=value
- A user-specified trimming factor, denoting the length
of trimmed lines in map units. All lines having a length
less than this trimming factor will be "trimmed" (i.e.,
removed) from the named vector input file.
Default: 10 (in units of meters or cells)
NOTES
v.support
must be run on the vector input file prior to
running v.trim.
v.support must
also be run on the resultant vector output file to
build the needed topology information stored under the
user's dig_plus directory.
r.line maintains the same format (binary or ASCII)
and attribute type (linear or area edge) as those of the
original vector (dig) input file.
A trimming factor of zero (0) will not remove any small
spurs, but will remove all excess nodes.
SEE ALSO
v.digit
v.import
v.support
parser
AUTHOR
Mike Baba
DBA Systems, Inc.
Last changed: $Date$