trusty (1) v.to.points.1grass.gz

NAME

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

KEYWORDS

       vector, geometry

SYNOPSIS

       v.to.points
       v.to.points help
       v.to.points  [-nvit] input=name output=name  [type=string[,string,...]]   [llayer=integer]   [dmax=float]
       [--overwrite]  [--verbose]  [--quiet]

   Flags:
       -n
           Write line nodes

       -v
           Write line vertices

       -i
           Interpolate points between line vertices

       -t
           Do not create attribute table

       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       input=name
           Input vector map containing lines

       output=name
           Output vector map where points will be written

       type=string[,string,...]
           Feature type
           Options: point,line,boundary,centroid,area
           Default: point,line,boundary,centroid

       llayer=integer
           Layer number
           Line layer
           Default: 1

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

DESCRIPTION

       v.to.points creates points along input lines. The output is a vector with 2 layers.  Layer  1  holds  the
       category  and  attributes  of  the  input  lines;  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.

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.

       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.  The  original  category  numbers  of  the   input
                     points/centroids  get  written to the 'lcat' attribute in layer 2 of the output vector. All
                     values for along are zero in the output vector, 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  -v  flag  is used to digitize points that fall on the line's vertices only.  dmax is ignored in this
       case.

       If the -i flag is used in conjunction with the -v flag, 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 switch 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
       d.vect t_powerlines_points

SEE ALSO

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

AUTHOR

       Radim Blazek

       Last changed: $Date: 2011-11-08 03:29:50 -0800 (Tue, 08 Nov 2011) $

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       © 2003-2013 GRASS Development Team