NAME

       r.to.vect  - Converts a raster map into a vector map layer.

KEYWORDS

       raster, conversion, vectorization

SYNOPSIS

       r.to.vect
       r.to.vect help
       r.to.vect [-svzbq] input=name output=name feature=string  [--overwrite]  [--verbose]  [--quiet]

   Flags:
       -s
           Smooth corners of area features

       -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.

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: 2008-05-16 12:09:06 -0700 (Fri, 16 May 2008) $

       Full index

       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                                    r.to.vect(1grass)