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

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) $

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