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NAME

r.skyview - Computes skyview factor visualization technique.

KEYWORDS

raster, visualization

SYNOPSIS

r.skyview
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]

Flags:

-o
Compute openness instead of skyview factor
Openness considers zenith angles > 90 degrees
-n
Invert color table for colorization raster
Ignored for input and color_input
--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 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
maxdistance=float
The maximum distance to consider when finding the horizon height
color_source=string
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
color_input=name
Custom raster map to be used for colorization
color_table=string
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_output=name
Colorized sky-view factor
basename=string
Set the basename for the intermediate maps

Table of contents

DESCRIPTION

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.

NOTES

Module r.horizon is used to compute elevation angles.

EXAMPLES

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

SEE ALSO

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

REFERENCES

AUTHORS

Anna Petrasova, NCSU GeoForAll

SOURCE CODE

Available at: r.skyview source code (history)


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© 2003-2020 GRASS Development Team, GRASS GIS 7.8.4dev Reference Manual