
NAME
r.to.vect.exe - Converts a raster map into a vector map layer.
KEYWORDS
raster
SYNOPSIS
r.to.vect.exe
r.to.vect.exe help
r.to.vect.exe [-svzbq] input=name output=name feature=string [--overwrite] [--verbose] [--quiet]
Flags:
- -s
- Smooth Corners
- -v
- Use raster values as categories instead of unique sequence (CELL only)
- -z
- Write raster values as z coordinate. Table is not created. Currently supported only for points
- -b
- Do not build vector topology (use with care for massive point export)
- -q
- Quiet - Do not show progress
- --overwrite
- Allow output files to overwrite existing files
- --verbose
- Verbose module output
- --quiet
- Quiet module output
Parameters:
- input=name
- Name of input raster map
- output=name
- Name for output vector map
- feature=string
- Feature type
- Options: point,line,area
- Default: line
DESCRIPTION
r.to.vect scans the named input raster map
layer, extracts points, lines or area edge features from it, converts data
to GRASS vector format.
Points
The r.to.vect program extracts data from a GRASS raster map layer and stores output
in a new GRASS vector file.
Lines
r.to.vect assumes that the input map has been thinned
using r.thin.
r.to.vect extracts vectors (aka, "arcs") from a
raster map. These arcs may represent linear features
(like roads or streams), or may represent area edge
features (like political boundaries, or soil mapping
units).
r.thin and r.to.vect
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.clean.
Areas
r.to.vect first traces the perimeter of each unique
area in the raster map layer and creates vector data to
represent it. The cell category values for the raster map
layer will be used to create attribute information for the
resultant vector area edge data.
A true vector tracing of the area edges might appear
blocky, since the vectors outline the edges of raster data
that are stored in rectangular cells. To produce a
better-looking vector map, r.to.vect smoothes the
corners of the vector data as they are being extracted. At
each change in direction (i.e., each corner), the two
midpoints of the corner cell (half the cell's height and
width) are taken, and the line segment connecting them is
used to outline this corner in the resultant vector map.
(The cell's cornermost node is ignored.) Because vectors
are smoothed by this program, the resulting vector map will
not be "true" to the raster map from which it was created.
The user should check the resolution of the geographic
region (and the original data) to estimate the possible
error introduced by smoothing.
r.to.vect extracts only area edges from the named raster input file.
If the raster map contains other data (i.e., line edges, or point data) the
output may be wrong.
BUGS
For feature=line the input raster map MUST be thinned by
r.thin;
if not, r.to.vect may crash.
Attributes are ignored for feature=line.
AUTHOR
Points
Bill Brown
Lines
Mike Baba
DBA Systems, Inc.
10560 Arrowhead Drive
Fairfax, Virginia 22030
Areas
Original version of r.poly:
Jean Ezell and Andrew Heekin,
U.S. Army Construction Engineering
Research Laboratory
Modified program for smoothed lines:
David Satnik,
Central Washington University
Updated 2001 by Andrea Aime, Modena, Italy
Update
Original r.to.sites, r.line and r.poly merged and updated to 5.7 by Radim Blazek
Last changed: $Date: 2007/02/12 17:49:11 $
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