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


       vector, geometry

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

           Write line nodes

           Write line vertices

           Interpolate points between line vertices

           Do not create attribute table

           Allow output files to overwrite existing files

           Verbose module output

           Quiet module output

           Input vector map containing lines

           Output vector map where points will be written

           Feature type
           Options: point,line,boundary,centroid,area
           Default: point,line,boundary,centroid

           Layer number
           Line layer
           Default: 1

           Maximum distance between points in map units
           Default: 100

DESCRIPTION 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.


       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, 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.


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




       Radim Blazek

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

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