.TH r.shaded.relief 1grass "" "GRASS 6.4.2" "Grass User's Manual"
.SH NAME
\fI\fBr.shaded.relief\fR\fR  - Creates shaded relief map from an elevation map (DEM).
.SH KEYWORDS
raster, elevation
.SH SYNOPSIS
\fBr.shaded.relief\fR
.br
\fBr.shaded.relief help\fR
.br
\fBr.shaded.relief map\fR=\fIstring\fR  [\fBshadedmap\fR=\fIstring\fR]   [\fBaltitude\fR=\fIfloat\fR]   [\fBazimuth\fR=\fIfloat\fR]   [\fBzmult\fR=\fIfloat\fR]   [\fBscale\fR=\fIfloat\fR]   [\fBunits\fR=\fIstring\fR]   [--\fBoverwrite\fR]  [--\fBverbose\fR]  [--\fBquiet\fR] 
.SS Flags:
.IP "\fB--overwrite\fR" 4m
.br
Allow output files to overwrite existing files
.IP "\fB--verbose\fR" 4m
.br
Verbose module output
.IP "\fB--quiet\fR" 4m
.br
Quiet module output
.PP
.SS Parameters:
.IP "\fBmap\fR=\fIstring\fR" 4m
.br
Input elevation map
.IP "\fBshadedmap\fR=\fIstring\fR" 4m
.br
Output shaded relief map name
.IP "\fBaltitude\fR=\fIfloat\fR" 4m
.br
Altitude of the sun in degrees above the horizon
.br
Options: \fI0-90\fR
.br
Default: \fI30\fR
.IP "\fBazimuth\fR=\fIfloat\fR" 4m
.br
Azimuth of the sun in degrees to the east of north
.br
Options: \fI0-360\fR
.br
Default: \fI270\fR
.IP "\fBzmult\fR=\fIfloat\fR" 4m
.br
Factor for exaggerating relief
.br
Default: \fI1\fR
.IP "\fBscale\fR=\fIfloat\fR" 4m
.br
Scale factor for converting horizontal units to elevation units
.br
Default: \fI1\fR
.IP "\fBunits\fR=\fIstring\fR" 4m
.br
Set scaling factor (applies to lat./long. locations only, none: scale=1)
.br
Options: \fInone,meters,feet\fR
.br
Default: \fInone\fR
.PP
.SH DESCRIPTION
\fIr.shaded.relief\fR creates a raster shaded relief map based on current
resolution settings and on sun altitude, azimuth, and z-exaggeration values
entered by the user. If no output shademap name is given, the new shaded
relief map is named \fI.shade\fR.
The map is assigned a grey-scale color table.
.PP
The module then prompts the user to enter values for:
..IP
.IP \fB1\fR
The \fBaltitude\fR of the sun in degrees above the horizon
(a value between 0 and 90 degrees), and
.IP \fB2\fR
The \fBazimuth\fR of the sun in degrees to the east of north
(a value between 0 and 360 degrees).
.IP \fB3\fR
The name of a raster map layer 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.
.IP \fB4\fR
The scaling parameter, which compensates for a different horizontal
\fBscale\fR than vertical scale. If 'scale' is a number then the ewres 
and nsres are multiplied by that scale to calculate the shading. (Default=1.0 
for equivalent horizontal and vertical scales.)
.IP \fB5\fR
For the special case when a latitude-longitude projection is used with an
elevation map measured in meters (e.g., SRTM, ETOPO2 etc.) or feet, the 
\fBunits\fR can be set to automatically set the horizontal scale to the the number of 
meters (scale=111120) or feet (scale=370400) in a degree of latitude. The script scales
latitude and longitude equally, so it's only approximately right, but for shading 
it's close enough. It makes the difference between a usable and unusable shade.
The \fBunits\fR parameter overrides the \fBscale\fR parameter.
.IP \fB6\fR
The \fBzmult\fR exaggeration factor that changes the apparent relief
for the shaded relief map.  This can be any positive (or negative) floating
point value. (Default=1.0)
.PP
Specifically, \fIr.shaded.relief\fR executes a \fIr.mapcalc\fR
statement. Refer to the manual entry for \fIr.mapcalc\fR for an explanation
of the filtering syntax shown in the above expression.
See, for example, the section on "The Neighborhood Modifier".
.PP
\fIr.shaded.relief\fR then runs \fIr.colors\fR
to assign a grey-scale color table to the new shaded relief map.
.SH NOTES
To visually improve the result of shade maps from low resolution elevation
models, use \fIr.resamp.interp\fR with bilinear or bicubic method to
resample the DEM at higher resolution. \fIr.shaded.relief\fR is then
run on the resampled DEM.
.SH EXAMPLES
In this example, the aspect map in the North Carolina sample
dataset location is used to hillshade the elevation map:
\fC
.DS
.br
g.region rast=elevation -p
.br
r.shaded.relief map=elevation shadedmap=elevation.shaded
.br
.DE
\fR
.PP
In Latitude-Longitude locations (or other non-metric locations), the
\fIscale\fR factor has to be used:
\fC
.DS
.br
# Latitude-Longitude example
.br
r.shaded.relief map=srtm shadedmap=srtm.shaded scale=111120
.br
.DE
\fR
.SH SEE ALSO
\(dq\fIr.mapcalc: An Algebra for GIS and Image Processing\fR", by Michael Shapiro
and Jim Westervelt, U.S. Army Construction Engineering Research Laboratory
(March/1991) (available from the GRASS web site).
.PP
\fI
d.his,
g.region,
r.blend,
r.colors,
r.mapcalc,
r.resamp.interp
\fR
.SH AUTHOR
Jim Westervelt, U.S. Army Construction Engineering 
Research Laboratory
.PP
\fILast changed: $Date: 2011-11-08 12:29:50 +0100 (Tue, 08 Nov 2011) $\fR
.PP
Full index
.PP
© 2003-2011 GRASS Development Team