NAME
r.line - Creates a new binary GRASS vector
(v.digit) file by
extracting linear features from a thinned raster file.
(GRASS Raster Program)
SYNOPSIS
r.line
r.line help
r.line input=name
output=name [type=name]
DESCRIPTION
r.line
scans the named raster map layer (input=name)
and extracts thinned linear features into the named vector file
(output=name).
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:
-
r.line input=name
output=name [type=name]
If the user specifies input raster and output vector map names
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 r.line on the command line,
without program arguments. In this case, the user will be prompted for
parameter values using the standard GRASS
parser interface.
Parameters:
- input=name
- Name of existing raster file to be used as input.
- output=name
- Name of new vector file to be output.
- type=name
- Line type of the extracted vectors; either line or area.
Specifying line will type extracted vectors as linear edges.
Specifying area will type extracted vectors as area edges.
Options: line or area
Default: type=line
r.line assumes that the input map has been thinned
using r.thin.
NOTES
r.line extracts vectors (aka, "arcs") from a
raster file. These arcs may represent linear features
(like roads or streams), or may represent area edge
features (like political boundaries, or soil mapping
units). The attribute type option allows the user
to establish the use of either linear or area edge
attributes for all of the extracted vectors.
r.poly
may be used to extract vectors that represent area features
(like soil mapping units, elevation ranges, etc.) from a raster file.
The user must run v.support
on the resultant vector
(v.digit)
files to build the dig_plus information.
r.thin and r.line
may create excessive nodes at every junction, and may create small spurs
or "dangling lines" during the thinning and vectorization process.
These excessive nodes and spurs may be removed using
v.trim.
BUGS
The input raster file MUST be thinned by
r.thin;
if not, r.line may crash.
SEE ALSO
r.poly
r.thin
v.digit
v.support
v.trim
parser
AUTHOR
Mike Baba
DBA Systems, Inc.
10560 Arrowhead Drive
Fairfax, Virginia 22030