v.to.points(1)

1v.to.points(1)                Grass User's Manual               v.to.points(1)
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NAME

6       v.to.points   -  Create  points  along input lines in new vector with 2
7       layers.
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KEYWORDS

10       vector, geometry
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SYNOPSIS

13       v.to.points
14       v.to.points help
15       v.to.points [-nvit] input=name output=name   [type=string[,string,...]]
16       [llayer=integer]   [dmax=float]   [--overwrite]  [--verbose]  [--quiet]
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18   Flags:
19       -n
20           Write line nodes
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22       -v
23           Write line vertices
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25       -i
26           Interpolate points between line vertices
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28       -t
29           Do not create attribute table
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31       --overwrite
32           Allow output files to overwrite existing files
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34       --verbose
35           Verbose module output
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37       --quiet
38           Quiet module output
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40   Parameters:
41       input=name
42           Input vector map containing lines
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44       output=name
45           Output vector map where points will be written
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47       type=string[,string,...]
48           Type
49           Feature type(s)
50           Options: point,line,boundary,centroid,area
51           Default: point,line,boundary,centroid
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53       llayer=integer
54           Layer number
55           Line layer
56           Default: 1
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58       dmax=float
59           Maximum distance between points in map units
60           Default: 100
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DESCRIPTION

63       v.to.points  creates  points  along input lines. The output is a vector
64       with 2 layers.  Layer 1 holds the category and attributes of the  input
65       lines;  all  points created along the same line have the same category,
66       equal to the category of that line. In layer  2  each  point  has  it's
67       unique category; other attributes stored in layer 2 are lcat - the cat‐
68       egory of the input line and along - the distance from line's start.
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NOTES

71       The dmax parameter is the maximum limit but not an exact  distance.  To
72       place  points with exact distance from the beginning of the vector line
73       the user should use v.segment.
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75       The type parameter is used to control which input vector geometry types
76       to convert into points.  Some caveats to consider about this parameter:
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78                     Points  and  centroids  can be considered as "lines" with
79                     only one node.  Consequently,  the  result  of  selecting
80                     point  or  centroid  as  the  type  parameter is that all
81                     points/centroids get written into the output vector.  The
82                     original  category  numbers of the input points/centroids
83                     get written to the 'lcat' attribute in  layer  2  of  the
84                     output  vector. All values for along are zero in the out‐
85                     put vector, as only point geometry  was  used  for  input
86                     (there  is no linear distance to calculate along, as each
87                     point/centroid is the start and end of its own "line".
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89                     Boundaries are treated  as  lines,  with  points  getting
90                     interpolated  along  the  boundary perimeter according to
91                     dmax. If  two  adjoining  polygons  share  a  topological
92                     boundary,  the  boundary  only  gets  converted to points
93                     once.
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95                     If the type paramter is set to area, the boundary of each
96                     area  is converted to points regardless of whether or not
97                     there is a topological boundary between  adjacent  areas.
98                     In  other  words,  the  common  boundary of two adjoining
99                     areas, for example, gets converted to points  twice.  The
100                     centroid is not converted to a point in the output vector
101                     for type=area.
102       The -v flag is used to digitize points that fall on the line's vertices
103       only.  dmax is ignored in this case.
104
105       If  the  -i  flag  is used in conjunction with the -v flag, v.to.points
106       will digitize points on the  line  vertices,  as  well  as  interpolate
107       points  between line vertices using dmax as the maximum allowable spac‐
108       ing.
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110       To get points created for the beginning, middle and end only,  use  the
111       -i switch and set dmax so that:
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113       (length of input line / 2) <= dmax <= length of input line
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115       So  if  dmax  is between 0.5x and 1.0x the line length, you will always
116       get points created at exactly the beginning,  middle  and  end  of  the
117       input line.
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EXAMPLE

120       In this example, the 't_powerlines' vector lines map in the Spearfish 6
121       location is used to create points along the input lines:
122       v.to.points in=t_powerlines out=t_powerlines_points dmax=120
123       d.vect t_powerlines_points
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AUTHOR

130       Radim Blazek
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132       Last changed: $Date: 2006-09-28 14:19:12 +0200 (Thu, 28 Sep 2006) $
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134       Full index
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136       © 2003-2008 GRASS Development Team
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140GRASS 6.3.0                                                     v.to.points(1)