v.perturb.1grass man page

v.perturb — Random location perturbations of vector points.


vector, geometry, statistics, random, point pattern


v.perturb --help
v.perturb [-b] input=name  [layer=string]  output=name  [distribution=string]  parameters=float[,float,...]  [minimum=float]   [seed=integer]   [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]



Do not build topology
Advantageous when handling a large number of points


Allow output files to overwrite existing files


Print usage summary


Verbose module output


Quiet module output


Force launching GUI dialog


input=name [required]

Name of input vector map
Or data source for direct OGR access


Layer number or name (’-1’ for all layers)
A single vector map can be connected to multiple database tables. This number determines which table to use. When used with direct OGR access this is the layer name.
Default: -1

output=name [required]

Name for output vector map


Distribution of perturbation
Options: uniform, normal
Default: uniform

parameters=float[,float,...] [required]

Parameter(s) of distribution
If the distribution is uniform, only one parameter, the maximum, is needed. For a normal distribution, two parameters, the mean and standard deviation, are required.


Minimum deviation in map units
Default: 0.0


Seed for random number generation
Default: 0


v.perturb reads a vector map of points and writes the same points but perturbs the eastings and northings by adding either a uniform or normal delta value. Perturbation means that a variating spatial deviation is added to the coordinates.


The uniform distribution is always centered about zero. The associated parameter is constrained to be positive and specifies the maximum of the distribution; the minimum is the negation of that parameter. Do perturb into a ring around the center, the minimum parameter can be used.

Usually, the mean (first parameter) of the normal distribution is zero (i.e., the distribution is centered at zero). The standard deviation (second parameter) is naturally constrained to be positive.

Output vector points are not guaranteed to be contained within the current geographic region.

See Also



James Darrell McCauley
when he was at: Agricultural Engineering Purdue University

Random number generators originally written in FORTRAN by Wes Peterson and translated to C using f2c.

Last changed: $Date: 2011-11-08 13:24:20 -0800 (Tue, 08 Nov 2011) $

Source Code

Available at: v.perturb source code (history)

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