.TH r.poly
.SH NAME
\fIr.poly\fR \- Extracts area edges from a raster map layer and converts
data to GRASS vector format.
.br
\fI(GRASS Raster Program)\fR
.SH SYNOPSIS
.B r.poly
.br
\fBr.poly help\fR
.br
\fBr.poly \fR[\fB-l\fR] \fBinput\*=\fIname\fR \fBoutput\*=\fIname\fR
.SH DESCRIPTION
\fIr.poly\fR
scans the named \fIinput\fR raster map layer, extracts area edge features
from it, converts data to GRASS vector format, and smoothes vectors.
.LP
\fIr.poly\fR 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.
.LP
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, \fIr.poly\fR 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 file.  (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.
.SH 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 and flag settings on the command line using the form:
.LP
.RS
\fBr.poly \fR[\fB-l\fR] \fBinput\*=\fIname\fR \fBoutput\*=\fIname\fR
.RE
.LP
Alternately, the user can simply type \fBr.poly\fR on the command line
without program arguments.  In this case, the user will be prompted for
parameter values and flag settings using the standard GRASS parser interface
described in the manual entry for \fIparser\fR.
.LP
\fBFlag:\fR
.IP \fB-l\fR 18
Smooth corners.

.LP
\fBParameters:\fR
.IP \fBinput\*=\fIname\fR 18
Use the existing raster map \fIname\fR as input.
.IP \fBoutput\*=\fIname\fR 18
Set the new vector output file name to \fIname\fR.
.SH NOTES
.I r.poly
extracts only area edges from the named raster input file.
If the raster file contains other data (i.e., line edges, or point data)
the output may be wrong.

The user must run \fIv.support\fR on the resultant file to build the needed
topology information stored in the \fIdig_plus\fR file.
.SH "SEE ALSO"
.I v.support
and
.I parser
.SH "AUTHOR"
\fIOriginal version of r.poly\fR:
.br
Jean Ezell, U.S. Army Construction Engineering Research Laboratory
.br
Andrew Heekin, U.S. Army Construction Engineering Research Laboratory
.LP
\fIModified program for smoothed lines\fR:
.br
David Satnik, Central Washington University, WA