GRASS logo

Note: A new GRASS GIS stable version has been released: GRASS GIS 7.6, available here.
Updated manual page: here

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

Table of contents

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 its 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:

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
Hence, 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 'railroads' vector lines map of the North Carolina sample dataset is used to create points along the input lines:
# The North Carolina data are metric.
# 200m distance for nodes (maximum limit but not an exact distance)
v.to.points railroads output=railroads_nodes use=node dmax=200

# verify the two layers in the resulting map
v.category railroads_nodes option=report

# vector info
v.info railroads_nodes

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: 2016-03-10 08:47:07 -0800 (Thu, 10 Mar 2016) $

SOURCE CODE

Available at: v.to.points source code (history)


Note: A new GRASS GIS stable version has been released: GRASS GIS 7.6, available here.
Updated manual page: here

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

© 2003-2019 GRASS Development Team, GRASS GIS 7.2.4svn Reference Manual