NAME

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

KEYWORDS

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

SYNOPSIS

       v.to.points
       v.to.points --help
       v.to.points  [-it]  input=name   [layer=string]    [type=string[,string,...]]  output=name
       [use=string]   [dmax=float]   [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -i
           Interpolate points between line vertices (only for use=vertex)

       -t
           Do not create attribute table

       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       input=name [required]
           Name of input vector map
           Or data source for direct OGR access

       layer=string
           Line layer number or name
           Vector features can have category values in different layers. This  number  determines
           which layer to use. When used with direct OGR access this is the layer name.
           Default: 1

       type=string[,string,...]
           Input feature type
           Options: point, line, boundary, centroid, area, face, kernel
           Default: point,line,boundary,centroid,face

       output=name [required]
           Name for output vector map

       use=string
           Use line nodes or vertices only
           Options: node, vertex

       dmax=float
           Maximum distance between points in map units
           Default: 100

DESCRIPTION

       v.to.points  creates  points  along  input  2D  or  3D  lines, boundaries and faces. Point
       features including centroids and kernels are copied from input vector map to  the  output.
       For details see notes about type parameter.

       The  output  is  a  vector  map  with  2  layers.  Layer 1 holds the category of the input
       features; all points created along the same line have the  same  category,  equal  to  the
       category  of  that  line. In layer 2 each point has it’s unique category; other attributes
       stored in layer 2 are lcat - the category of the input line and along - the distance  from
       line’s start.

       By default only features with category are processed, see layer parameter for details.

NOTES

       The  dmax  parameter  is the maximum limit but not an exact distance. To place points with
       exact distance from the beginning of the vector line the user should use v.segment.

       Set layer to -1 to process features from all layers including features  without  category.
       Features will be assigned new unique categories at layer 1. Option layer=-1 should be used
       to convert boundaries, as in most of cases boundaries lack category values.

       The type parameter is used to control which input vector geometry types  to  convert  into
       points. Some caveats to consider about this parameter:

           •   Points   and   centroids  can  be  considered  as  "lines"  with  only  one  node.
               Consequently, the result of selecting point or centroid as the type  parameter  is
               that  all  points/centroids  get  written into the output vector map. The original
               category numbers of the input points/centroids get written to the ’lcat’ attribute
               in  layer  2 of the output vector map. All values for along are zero in the output
               vector map, as only point geometry was used for input (there is no linear distance
               to  calculate  along,  as  each  point/centroid  is  the  start and end of its own
               "line").

           •   Boundaries are treated as  lines,  with  points  getting  interpolated  along  the
               boundary   perimeter  according  to  dmax.  If  two  adjoining  polygons  share  a
               topological boundary, the boundary only gets converted to points once.

           •   If the type parameter is set to area, the boundary of each area  is  converted  to
               points  regardless  of  whether  or  not  there  is a topological boundary between
               adjacent areas. In other words, the common boundary of two  adjoining  areas,  for
               example,  gets converted to points twice. The centroid is not converted to a point
               in the output vector for type=area.

       The use=vertex option is used to digitize points that fall on the  line’s  vertices  only.
       Parameter  dmax  is  ignored in this case. Similarly to use=node when only line’s node are
       used.

       If the -i flag is used  in  conjunction  with  the  use=vertex  option,  v.to.points  will
       digitize  points on the line vertices, as well as interpolate points between line vertices
       using dmax as the maximum allowable spacing.

       To get points created for the beginning, middle and end only, use the -i flag and set dmax
       so that:
        (length of input line / 2) <= dmax <= length of input line
       So if dmax is between 0.5x and 1.0x the line length, you will always get points created at
       exactly the beginning, middle and end of the input line.

EXAMPLE

       In this example, the ’t_powerlines’ vector lines map in the Spearfish 6 location  is  used
       to create points along the input lines:
       v.to.points in=t_powerlines out=t_powerlines_points dmax=120

SEE ALSO

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

AUTHOR

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

       Last changed: $Date: 2014-11-28 16:46:08 +0100 (Fri, 28 Nov 2014) $

       Main index | Vector index | Topics index | Keywords index | Full index

       © 2003-2016 GRASS Development Team, GRASS GIS 7.0.3 Reference Manual