1r.to.vect(1) Grass User's Manual r.to.vect(1)
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6 r.to.vect - Converts a raster map into a vector map layer.
7
9 raster
10
12 r.to.vect
13 r.to.vect help
14 r.to.vect [-svzbq] input=string output=name feature=string [--over‐
15 write]
16 Flags:
18 -s Smooth Corners
19 -v Use raster values as categories instead of unique sequence (CELL
21 only)
22 -z Write raster values as z coordinate. Table is not created. Cur‐
24 rently supported only for points
25 -b Do not build vector topology (use with care for massive point
27 export)
28 -q Quiet - Do not show progress
30 --overwrite
32 Parameters:
34 input=string
35 raster input file
36 output=name
38 Name for output vector map
39 feature=string
41 Feature type Options: point,line,area Default: line
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44 r.to.vect scans the named input raster map layer, extracts points,
45 lines or area edge features from it, converts data to GRASS vector for‐
46 mat.
47 Points
49 The r.to.vect program extracts data from a GRASS raster map layer and
50 stores output in a new GRASS vector file.
51 Lines
53 r.to.vect assumes that the input map has been thinned using r.thin.
54 r.to.vect extracts vectors (aka, "arcs") from a raster file. These
56 arcs may represent linear features (like roads or streams), or may rep‐
57 resent area edge features (like political boundaries, or soil mapping
58 units).
59 r.thin and r.to.vect may create excessive nodes at every junction, and
61 may create small spurs or "dangling lines" during the thinning and vec‐
62 torization process. These excessive nodes and spurs may be removed
63 using v.clean.
64 Areas
66 r.to.vect first traces the perimeter of each unique area in the raster
67 map layer and creates vector data to represent it. The cell category
68 values for the raster map layer will be used to create attribute infor‐
69 mation for the resultant vector area edge data.
70 A true vector tracing of the area edges might appear blocky, since the
72 vectors outline the edges of raster data that are stored in rectangular
73 cells. To produce a better-looking vector map, r.to.vect smoothes the
74 corners of the vector data as they are being extracted. At each change
75 in direction (i.e., each corner), the two midpoints of the corner cell
76 (half the cell's height and width) are taken, and the line segment con‐
77 necting them is used to outline this corner in the resultant vector
78 file. (The cell's cornermost node is ignored.) Because vectors are
79 smoothed by this program, the resulting vector map will not be "true"
80 to the raster map from which it was created. The user should check the
81 resolution of the geographic region (and the original data) to estimate
82 the possible error introduced by smoothing.
83 r.to.vect extracts only area edges from the named raster input file.
85 If the raster file contains other data (i.e., line edges, or point
86 data) the output may be wrong.
87
89 For feature=line the input raster file MUST be thinned by r.thin; if
90 not, r.to.vect may crash.
91 Attributes are ignored for feature=line.
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95 Points
96 Bill Brown
97 Lines
98 Mike Baba
99 DBA Systems, Inc.
100 10560 Arrowhead Drive
101 Fairfax, Virginia 22030
102 Areas
103 Original version of r.poly:
104 Jean Ezell and Andrew Heekin,
105 U.S. Army Construction Engineering Research Laboratory
106 Modified program for smoothed lines:
108 David Satnik, Central Washington University
109 Updated 2001 by Andrea Aime, Modena, Italy
110 Update
111 Original r.to.sites, r.line and r.poly merged and updated to 5.7 by
112 Radim Blazek
113 Last changed: $Date: 2007/02/12 17:49:41 $
115 Full index
117GRASS 6.2.2 r.to.vect(1)