**--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

**elevation**=*name[,**name*,...]**[required]**- DEM Raster Input
- GRASS raster elevation map
**size**=*integer[,**integer*,...]- Size of neighbourhood
- Size of neighbourhood to calculate the vector dispersion over. Multiple sizes are accepted to more efficiently calculate the VRM over different scales.
- Default:
*3* **output**=*name[,**name*,...]**[required]**- Vector Ruggedness Measure Output
- Name for output raster map(s)
**slope**=*name*- Optional slope raster map
- Optional slope raster map. If not supplied, then a slope map will be calculated internally.
**aspect**=*name*- Optional aspect raster map
- Optional aspect raster map. If not supplied, then an aspect map will be calculated internally.
**exponent**=*float*- Exponent for distance weighting (zero is equal weights)
- Default:
*0* **nprocs**=*integer*- The maximum number of cores to use for multiprocessing
- The maximum number of cores to use for multiprocessing. -1 uses all cores, -2 uses n_cores-1 etc.
- Default:
*-1*

*r.vector.ruggedness* represents a measurement of terrain ruggedness based on the methodology conceived by
Sappington et al. (2007). The measure is calculated by decomposing slope and aspect into 3-dimensional vectors, and
calculating the resultant vector magnitude within a user-specified moving window size using *r.neighbors*. The
user can specify neighborhood size to measure ruggedness across larger scales. Neighborhood operations are
performed using a rectangular window shape.

The *r.vector.ruggedness* tool provides an efficient approach of calculating the Vector Ruggedness Measure over
multiple window sizes. The *size* argument accepts multiple answers (as a comma separated list), which will
cause the tool to reuse the same slope, aspect and vector calculations, and apply them to the neighborhood
operations that calculate the vector magnitudes. By default, both the calculation of the vectors and the vector
magnitudes, including over different window sizes is performed in parallel using all available cores. To restrict
parallel processing, the *nprocs* argument can be changed to use a smaller number of processing cores. When
multiple sizes are used, the *output* raster name is appended with the window size. Optionally, pre-calculated
slope and aspect maps (in degrees) can be used in the *slope* and *aspect* arguments to save
computational time if the maps are already available.

This script was adapted from the original Sappington et al. (2007) script.

The examples are to be executed using the GRASS GIS sample North Carolina data set. To calculate the Vector Ruggedness Measure using a single neighborhood size:

r.vector.ruggedness elevation=elevation size=3 output=vrm

For efficient calculations of the Vector Ruggedness Measure over multiple neighborhood sizes, the slope, aspect and their x, y, z vectors will be reused during the calculation. The output name will be appended with the neighborhood size in order to identify the output maps:

r.vector.ruggedness elevation=elevation size=3,5,7,9,11 output=vrm

Available at: r.vector.ruggedness source code (history)

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