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

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

10       vector, geometry, 3D, line, node, vertex, point
11

SYNOPSIS

13       v.to.points
14       v.to.points --help
15       v.to.points         [-iprt]         input=name           [layer=string]
16       [type=string[,string,...]]   output=name   [use=string]    [dmax=float]
17       [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]
18
19   Flags:
20       -i
21           Interpolate points between line vertices (only for use=vertex)
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23       -p
24           Use dmax as percentage of line length
25
26       -r
27           Start from the end node
28
29       -t
30           Do not create attribute table
31
32       --overwrite
33           Allow output files to overwrite existing files
34
35       --help
36           Print usage summary
37
38       --verbose
39           Verbose module output
40
41       --quiet
42           Quiet module output
43
44       --ui
45           Force launching GUI dialog
46
47   Parameters:
48       input=name [required]
49           Name of input vector map
50           Or data source for direct OGR access
51
52       layer=string
53           Line layer number or name
54           Vector features can have category values in different layers.  This
55           number  determines  which  layer  to use. When used with direct OGR
56           access this is the layer name.
57           Default: 1
58
59       type=string[,string,...]
60           Input feature type
61           Options: point, line, boundary, centroid, area, face, kernel
62           Default: point,line,boundary,centroid,face
63
64       output=name [required]
65           Name for output vector map
66
67       use=string
68           Use line nodes (start/end) or vertices only
69           Options: node, start, end, vertex
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71       dmax=float
72           Maximum distance between points in map units or percentage with -p
73           Default: 100
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DESCRIPTION

76       v.to.points creates points along input 2D or 3D lines,  boundaries  and
77       faces.  Point  features including centroids and kernels are copied from
78       input vector map to the output. For details see notes about type param‐
79       eter.
80
81       The output is a vector map with 2 layers. Layer 1 holds the category of
82       the input features; all points created along the  same  line  have  the
83       same  category,  equal  to  the  category of that line. In layer 2 each
84       point has its unique category; other attributes stored in layer  2  are
85       lcat  -  the  category  of the input line and along - the distance from
86       line’s start.
87
88       By default only features with category are processed, see layer parame‐
89       ter for details.
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NOTES

92       The  dmax  parameter is the maximum limit but not an exact distance. To
93       place points with exact distance from the beginning of the vector  line
94       the user should use v.segment.
95
96       Set  layer to -1 to process features from all layers including features
97       without category. Features will be assigned new  unique  categories  at
98       layer  1.  Option  layer=-1 should be used to convert boundaries, as in
99       most of cases boundaries lack category values.
100
101       The type parameter is used to control which input vector geometry types
102       to convert into points. Some caveats to consider about this parameter:
103
104           ·   Points and centroids can be considered as "lines" with only one
105               node. Consequently, the result of selecting point  or  centroid
106               as  the type parameter is that all points/centroids get written
107               into the output vector map. The original  category  numbers  of
108               the  input points/centroids get written to the ’lcat’ attribute
109               in layer 2 of the output vector map. All values for  along  are
110               zero  in the output vector map, as only point geometry was used
111               for input (there is no linear distance to calculate  along,  as
112               each point/centroid is the start and end of its own "line").
113
114           ·   Boundaries  are  treated as lines, with points getting interpo‐
115               lated along the boundary perimeter according to  dmax.  If  two
116               adjoining  polygons  share a topological boundary, the boundary
117               only gets converted to points once.
118
119           ·   If the type parameter is set to area, the boundary of each area
120               is  converted to points regardless of whether or not there is a
121               topological boundary between adjacent areas.  In  other  words,
122               the  common  boundary of two adjoining areas, for example, gets
123               converted to points twice. The centroid is not converted  to  a
124               point in the output vector for type=area.
125
126       The  use=vertex  option  is  used  to  digitize points that fall on the
127       line’s vertices only. Parameter dmax is ignored in this case. Similarly
128       to  use=node  when  only  line’s  node  are used. To filter only start‐
129       ing/ending nodes use use=start/end.
130
131       If the -i flag is used  in  conjunction  with  the  use=vertex  option,
132       v.to.points  will  digitize  points  on  the  line vertices, as well as
133       interpolate points between line vertices  using  dmax  as  the  maximum
134       allowable spacing.
135
136       Use the -p flag to treat dmax as a percentage of each line length.  For
137       example, to get points created for the beginning, middle and end  only,
138       use the -p flag and set dmax so that:
139        50 < dmax <= 100
140       Hence,  if  dmax  is  between  0.5x  and 1.0x the line length, you will
141       always get points created at exactly the beginning, middle and  end  of
142       the input line.
143
144       Use the -r flag to create points starting from the end node.
145

EXAMPLES

147   Points along the input lines
148       In this example, the ’railroads’ vector lines map of the North Carolina
149       sample dataset is used to create points along the input lines:
150       # The North Carolina data are metric.
151       # 200m distance for points (maximum limit but not an exact distance)
152       v.to.points input=railroads output=railroads_points dmax=200
153       # verify the two layers in the resulting map
154       v.category input=railroads_points option=report
155       # vector info
156       v.info map=railroads_points
157
158   Extract nodes as points
159       v.to.points input=railroads output=railroads_nodes use=node
160
161   Extract starting/ending nodes as points
162       v.to.points input=railroads output=railroads_start use=start
163       v.to.points input=railroads output=railroads_end use=end
164

SEE ALSO

166        v.segment, v.split, v.to.rast, v.to.db
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AUTHOR

169       Radim Blazek
170       Updated to GRASS 7 by  Martin  Landa,  Czech  Technical  University  in
171       Prague, Czech Republic
172

SOURCE CODE

174       Available at: v.to.points source code (history)
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176       Main  index  | Vector index | Topics index | Keywords index | Graphical
177       index | Full index
178
179       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual
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183GRASS 7.8.2                                                     v.to.points(1)
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