NAME
r.shaded.relief - Creates shaded relief map from an elevation map (DEM).
SYNOPSIS
r.shaded.relief
r.shaded.relief help
r.shaded.relief map=string altitude=integer azimuth=integer [units=string]
Parameters:
- map=string
- Elevation map (Name CANNOT contain dashes '-' or dots '.').
- altitude=integer
- Altitude of the sun in degrees above the horizon (must be 1-89).
- Default: 30
- azimuth=integer
- Azimuth of the sun in degrees to the east of north (must be 0-360).
- Default: 270
- units=string
- Elevation map units.
- Options: meters,feet
- Default: meters
DESCRIPTION
r.shaded.relief is a Bourne shell (sh(1)) script that
creates a raster shaded relief map based on current
resolution settings and on sun altitude and azimuth values
entered by the user. The new shaded relief map is
named <elevation>.shade and stored in the user's current
mapset. The map is assigned a grey-scale color table.
If no parameters are provided on startup, this program is interactive;
thus if the user enters the command:
-
r.shaded.relief
The program then prompts the user to enter values for:
- The altitude of the sun in degrees above the horizon
(a value between 0 and 90 degrees), and
- The azimuth of the sun in degrees to the east of north
(a value between 0 and 360 degrees).
- The name of a raster map layer whose cell category values are to
provide elevation values for the shaded relief map. Typically, this
would be a map layer of elevation; however, any raster map layer
can be named.
- The scaling parameter, which compensates for a different horizontal
scale than vertical scale.
For example, when a latitude-longitude projection is used with an elevation
map measured in meters.
If 'scale' is a number then the ewres and nsres are multiplied by that
scale to calculate the shading. If 'scale' is 'meters' the number of
meters in a degree of latitude is used as the scale.
If 'scale' is 'feet' then the number of feet in a degree is used.
The script scales latitude and longitude equally, so
it's only approximately right, but for shading its close enough. It makes
the difference between a usable and unusable shade.
Specifically, r.shaded.relief executes a
r.mapcalc
statement. Refer to the manual entry for
r.mapcalc for an explanation
of the filtering syntax shown in the above expression.
See, for example, the section on "The Neighborhood Modifier".
r.shaded.relief then runs r.colors
to assign a grey-scale color table to the new shaded relief map.
FILES
This program is simply a shell script. Users are encouraged to make their
own shell scripts using similar techniques.
See $GISBASE/scripts/r.shaded.relief.
SEE ALSO
An Algebra for GIS and Image Processing, by Michael Shapiro and Jim
Westervelt, U.S. Army Construction Engineering Research Laboratory
(March/1991) (get from GRASS web site).
shade.clr.sh
blend.sh
g.ask
g.region
r.colors
r.mapcalc
AUTHOR
Jim Westervelt, U.S. Army Construction Engineering
Research Laboratory
Last changed: $Date: 2004/05/15 13:48:04 $
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