1v.clean(1)                    Grass User's Manual                   v.clean(1)
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NAME

6       v.clean  - Toolset to clean vector topology
7

KEYWORDS

9       vector
10

SYNOPSIS

12       v.clean
13       v.clean help
14       v.clean   [-b]   input=name   output=name    [type=string[,string,...]]
15       [error=name]    tool=string[,string,...]     [thresh=float[,float,...]]
16       [--overwrite]
17
18   Flags:
19       -b  Do not rebuild and store the topology at the end
20
21       --overwrite
22
23   Parameters:
24       input=name
25           Name of input vector map
26
27       output=name
28           Name for output vector map
29
30       type=string[,string,...]
31           Type     Options:     point,line,boundary,centroid,area    Default:
32           point,line,boundary,centroid,area
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34       error=name
35           Name of output map where errors are written
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37       tool=string[,string,...]
38           Cleaning      tool      Options:       break,rmdupl,rmdangle,chdan‐
39           gle,rmbridge,chbridge,snap,rmdac,bpol,prune,rmarea,rmsa      break:
40           break lines at each intersection  rmdupl:  remove  duplicate  lines
41           (pay attention to categories!)  rmdangle: remove dangles, threshold
42           ignored if < 0 chdangle: change the  type  of  boundary  dangle  to
43           line,  threshold  ignored  if  <  0,  input  line  type  is ignored
44           rmbridge: remove bridges connecting area and island  or  2  islands
45           chbridge:  change the type of bridges connecting area and island or
46           2 islands from boundary to line  snap:  snap  lines  to  vertex  in
47           threshold  rmdac:  remove  duplicate  area centroids ('type' option
48           ignored) bpol: break (topologically clean) polygons (imported  from
49           non  topological  format (like shapefile). Boundaries are broken on
50           each point shared between 2 and more polygons where angles of  seg‐
51           ments  are different prune: remove vertices in threshold from lines
52           and boundaries, boundary is pruned only if topology is not  damaged
53           (new intersection, changed attachement of centroid), first and last
54           segment of the boundary  is  never  changed  rmarea:  remove  small
55           areas,  the  longest  boundary  with adjacent area is removed rmsa:
56           remove small angles between lines at nodes
57
58       thresh=float[,float,...]
59           Threshold Threshold in map units, one value for each tool (default:
60           0.0[,0.0,...])
61

DESCRIPTION

63       v.clean allows the user to automatically fix topology of vector files.
64

NOTES

66       The  user does not have to run v.build on the output vector, unless the
67       -b flag was used. The -b flag affects only the output vector - topology
68       is always built for error vector.
69
70   Removing small angles between lines at nodes
71       The  rmsa  tool only concerns angles which are so small that the calcu‐
72       lated angle is 0. The user cannot change this threshold. The  following
73       figure should help to understand what the tool does.
74
75   What is a bridge?
76       A bridge is an area type connection of an island (polygon in a polygon)
77       to the outer polygon. This is topologically incorrect (but  OGC  Simple
78       Features  allow  it). v.clean can be used to optionally change the line
79       type to fulfill the topology rules or to remove  the  bridge  from  the
80       map:
81           +-------------+             +-------------+   +-------------+
82           |            P|  P: polygon |            P|   |            P|
83           |    +---+    |  I: island  |    +---+    |   |    +---+    |
84           |    | I |    |  B: bridge  |    | I |    |   |    | I |    |
85           |    |   |    |  L: line    |    |   |    |   |    |   |    |
86           |    +-+-+    |             |    +---+    |   |    +-.-+    |
87           |      |      |             |             |   |      .      |
88           |      | B    |             |             |   |      . L    |
89           |      |      |             |             |   |      .      |
90           +------+------+             +-------------+   +-------------+
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92

EXAMPLES

94   Snap lines to vertex in threshold
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96       v.clean input=testmap output=cleanmap tool=snap thresh=1
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99   Cleaning OGR imported data (Simple Feature data)
100       The  import of areas with v.in.ogr requires a subsequent run of v.clean
101       to update the map to a topologically valid structure (removal of dupli‐
102       cate  collinear  lines  etc).  The tools used for that are 'rmdupl' and
103       'bpol':
104       v.clean input=areamap output=areamap_clean tool=rmdupl,bpol
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106
107   Extracting intersection points of vector lines
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109       v.clean input=lines1 output=lines2 err=points tool=break
110        Intersection points are written to 'points' map.
111
112   Break lines
113       v.clean will break the lines where they cross,  creating  new  node  if
114       needed. Example:
115       v.in.ascii -n out=crossed_lines format=standard << EOF
116       L 2
117        0 5
118        10 5
119       L 2
120        5 0
121        5 10
122       EOF
123       v.clean in=crossed_lines out=crossed_lines_brk \
124               error=intersection tool=break
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AUTHORS

128       David Gerdes, U.S. Army Construction Engineering Research Laboratory
129       Radim Blazek, ITC-Irst, Trento, Italy
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131       Last changed: $Date: 2006/09/29 21:22:55 $
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133       Full index
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137GRASS 6.2.2                                                         v.clean(1)