1r.to.vect(1)                  Grass User's Manual                 r.to.vect(1)
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NAME

6       r.to.vect  - Converts a raster map into a vector map.
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KEYWORDS

9       raster, conversion, geometry, vectorization
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SYNOPSIS

12       r.to.vect
13       r.to.vect --help
14       r.to.vect  [-svzbt]  input=name  output=name type=string  [column=name]
15       [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]
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17   Flags:
18       -s
19           Smooth corners of area features
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21       -v
22           Use raster values as categories instead of  unique  sequence  (CELL
23           only)
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25       -z
26           Write raster values as z coordinate
27           Table is not created. Currently supported only for points.
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29       -b
30           Do not build vector topology
31           Recommended for massive point conversion
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33       -t
34           Do not create attribute table
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36       --overwrite
37           Allow output files to overwrite existing files
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39       --help
40           Print usage summary
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42       --verbose
43           Verbose module output
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45       --quiet
46           Quiet module output
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48       --ui
49           Force launching GUI dialog
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51   Parameters:
52       input=name [required]
53           Name of input raster map
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55       output=name [required]
56           Name for output vector map
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58       type=string [required]
59           Output feature type
60           Options: point, line, area
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62       column=name
63           Name of attribute column to store value
64           Name must be SQL compliant
65           Default: value
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DESCRIPTION

68       r.to.vect  scans  the  named  input  raster map layer, extracts points,
69       lines or area edge features from it, converts data to GRASS vector for‐
70       mat.
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72   Point conversion
73       The  r.to.vect  program extracts data from a GRASS raster map layer and
74       stores output in a new GRASS vector file.
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76   Line conversion
77       r.to.vect assumes that the input map has been thinned using r.thin.
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79       r.to.vect extracts vectors (aka, "arcs") from a raster map.  These arcs
80       may represent linear features (like roads or streams), or may represent
81       area edge features (like political boundaries, or soil mapping units).
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83       r.thin and r.to.vect may create excessive nodes at every junction,  and
84       may create small spurs or "dangling lines" during the thinning and vec‐
85       torization process.  These excessive nodes and  spurs  may  be  removed
86       using v.clean.
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88   Area conversion
89       r.to.vect  first traces the perimeter of each unique area in the raster
90       map layer and creates vector data to represent it.  The  cell  category
91       values for the raster map layer will be used to create attribute infor‐
92       mation for the resultant vector area edge data.
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94       A true vector tracing of the area edges might appear blocky, since  the
95       vectors outline the edges of raster data that are stored in rectangular
96       cells. To produce a better-looking vector map, r.to.vect  smoothes  the
97       corners  of the vector data as they are being extracted. At each change
98       in direction (i.e., each corner), the two midpoints of the corner  cell
99       (half the cell’s height and width) are taken, and the line segment con‐
100       necting them is used to outline this corner  in  the  resultant  vector
101       map.   (The  cell’s  cornermost  node  is ignored.) Because vectors are
102       smoothed by this program, the resulting vector map will not  be  "true"
103       to the raster map from which it was created.  The user should check the
104       resolution of the geographic region (and the original data) to estimate
105       the possible error introduced by smoothing.
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107       r.to.vect extracts only area edges from the named raster input file. If
108       the raster map contains other data (i.e., line edges,  or  point  data)
109       the output may be wrong.
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EXAMPLES

112       The examples are based on the North Carolina sample dataset:
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114       Conversion of raster points to vector points:
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116       Random sampling of points:
117       g.region raster=elevation -p
118       # random sampling of points (note that r.random also writes vector points)
119       r.random elevation raster_output=elevrand1000 n=1000
120       r.to.vect input=elevrand1000 output=elevrand1000 type=point
121       # univariate statistics of sample points
122       v.univar elevrand1000 column=value type=point
123       # compare to univariate statistics on original full raster map
124       r.univar elevation
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126       Conversion of raster lines to vector lines:
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128       Vectorization of streams in watershed basins map:
129       g.region raster=elevation -p
130       r.watershed elev=elevation stream=elev.streams thresh=50000
131       r.to.vect -s input=elev.streams output=elev_streams type=line
132       # drop "label" column which is superfluous in this example
133       v.db.dropcolumn map=elev_streams column=label
134       v.db.renamecolumn map=elev_streams column=value,basin_id
135       # report length per basin ID
136       v.report map=elev_streams option=length units=meters sort=asc
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138       Conversion of raster polygons to vector polygons:
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140       Vectorization of simplified landuse class map:
141       g.region raster=landclass96 -p
142       # we smooth corners of area features
143       r.to.vect -s input=landclass96 output=my_landclass96 type=area
144       v.colors my_landclass96 color=random
145

KNOWN ISSUES

147       For  type=line  the input raster map MUST be thinned by r.thin; if not,
148       r.to.vect may crash.
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SEE ALSO

151        g.region, r.thin, v.clean
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AUTHORS

154       Point support
155       Bill Brown
156       Line support
157       Mike Baba
158       DBA Systems, Inc.
159       10560 Arrowhead Drive
160       Fairfax, Virginia 22030
161       Area support
162       Original version of r.poly:
163       Jean Ezell and Andrew Heekin,
164       U.S. Army Construction Engineering Research Laboratory
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166       Modified program for smoothed lines:
167       David Satnik, Central Washington University
168       Updated 2001 by Andrea Aime, Modena, Italy
169       Update
170       Original r.to.sites, r.line and r.poly merged and  updated  to  5.7  by
171       Radim Blazek
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SOURCE CODE

174       Available at: r.to.vect source code (history)
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176       Main  index  | Raster index | Topics index | Keywords index | Graphical
177       index | Full index
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179       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual
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183GRASS 7.8.2                                                       r.to.vect(1)
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