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Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current manual page.


r.skyview - Computes skyview factor visualization technique.


raster, visualization


r.skyview --help
r.skyview [-on] input=name output=name ndir=integer [maxdistance=float] [color_source=string] [color_input=name] [color_table=string] [colorized_output=name] [basename=string] [--overwrite] [--help] [--verbose] [--quiet] [--ui]


Compute openness instead of skyview factor
Openness considers zenith angles > 90 degrees
Invert color table for colorization raster
Ignored for input and color_input
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 raster map
output=name [required]
Name for output raster map
ndir=integer [required]
Number of directions (8 to 32 recommended)
Options: 2-360
Default: 16
The maximum distance to consider when finding the horizon height
Source raster for colorization
Input and color_input are taken from input and color_input options respectively. The rest is computed using r.slope.aspect
Options: input, color_input, slope, aspect, dxy
Default: input
input: use the raster from the input option
color_input: use the raster from the color_input option
slope: compute and use slope
aspect: compute and use aspect
dxy: compute and use second order partial derivative dxy
Custom raster map to be used for colorization
Color table for colorization raster (preset color table by default)
If empty, the color table of the created raster is used (not used at all for input and color_input)
Options: reds, blues, greens, oranges, sepia, aspectcolr
Colorized sky-view factor
Set the basename for the intermediate maps

Table of contents


Module r.skyview computes skyview factor, a relief visualization technique (Zaksek et al. 2011). The value of each cell is given by the portion of visible sky (from that cell) limited by the surrounding relief. The values range from 0 to 1. The lighter the value is, the more open the terrain is.

When flag -o is set, r.skyview computes openness instead of skyview factor. Openness (based on positive openness by Yokoyama et al. 2002) takes into account zenith angles greater than 90 degrees, while skyview limits zenith angles to 90 degrees (celestial hemisphere). This makes difference for example for visualization of horizontal planes and slopes. Openness values range from 0 to 2.


Module r.horizon is used to compute elevation angles.


We compute the skyview factor map of the North Carolina sample dataset elevation map:
g.region raster=elevation
r.skyview input=elevation output=elevation_skyview ndir=8
Skyview factor example


r.horizon, r.relief, r.shaded.pca, r.local.relief



Anna Petrasova, NCSU GeoForAll


Available at: r.skyview source code (history)

Latest change: Wednesday Mar 30 10:17:35 2022 in commit: 25b0a9981b66c443a1c1af1d5f26182c93268b45

Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current manual page.

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