.TH r.relief 1grass "" "GRASS 7.8.5" "GRASS GIS User's Manual"
.SH NAME
\fI\fBr.relief\fR\fR  \- Creates shaded relief map from an elevation map (DEM).
.br
.SH KEYWORDS
raster, elevation, relief, terrain, hillshade
.SH SYNOPSIS
\fBr.relief\fR
.br
\fBr.relief \-\-help\fR
.br
\fBr.relief\fR \fBinput\fR=\fIname\fR \fBoutput\fR=\fIname\fR  [\fBaltitude\fR=\fIfloat\fR]   [\fBazimuth\fR=\fIfloat\fR]   [\fBzscale\fR=\fIfloat\fR]   [\fBscale\fR=\fIfloat\fR]   [\fBunits\fR=\fIstring\fR]   [\-\-\fBoverwrite\fR]  [\-\-\fBhelp\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR]  [\-\-\fBui\fR]
.SS Flags:
.IP "\fB\-\-overwrite\fR" 4m
.br
Allow output files to overwrite existing files
.IP "\fB\-\-help\fR" 4m
.br
Print usage summary
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.IP "\fB\-\-ui\fR" 4m
.br
Force launching GUI dialog
.SS Parameters:
.IP "\fBinput\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name of input raster (typically elevation) map
.IP "\fBoutput\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name for output shaded relief map
.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 "\fBzscale\fR=\fIfloat\fR" 4m
.br
Factor for exaggerating relief
.br
Default: \fI1\fR
.IP "\fBscale\fR=\fIfloat\fR" 4m
.br
Scale factor for converting meters to elevation units
.br
Default: \fI1\fR
.IP "\fBunits\fR=\fIstring\fR" 4m
.br
Elevation units (overrides scale factor)
.br
Options: \fIintl, survey\fR
.br
\fBintl\fR: international feet
.br
\fBsurvey\fR: survey feet
.SH DESCRIPTION
\fIr.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.
.PP
The parameters controlling the shading are:
.IP
.IP \fB1\fR
An \fBinput\fR raster map 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 \fB2\fR
The \fBaltitude\fR of the sun in degrees above the horizon
(a value between 0 and 90 degrees).
.IP \fB3\fR
The \fBazimuth\fR of the sun in degrees to the east of north (a
value between 0 and 360 degrees; clockwise from north)
.IP \fB4\fR
The scaling parameter, which compensates for a different
horizontal \fBscale\fR than vertical scale. If \fBscale\fR 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
The \fBzscale\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)
.IP \fB6\fR
Horizontal distances are calculated in meters, using geodesic
distances for a latitude\-longitude projection. With an elevation map
measured in feet, the \fBunits\fR option can be set to automatically
convert meters to international feet (0.3048 meters = 1 foot) or survey
feet (1200 / 3937 meters = 1 foot). The \fBunits\fR parameter overrides
the \fBscale\fR parameter.
.PP
.PP
\fIr.relief\fR assigns 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.relief\fR is then run on the resampled DEM.
.PP
The current mask is ignored.
.SH EXAMPLES
.SS Shaded relief map
In this example, the aspect map in the North Carolina sample
dataset location is used to hillshade the elevation map:
.br
.nf
\fC
g.region raster=elevation \-p
r.relief input=elevation output=elevation_shade
\fR
.fi
.br
\fIr.relief: shaded elevation map (subset)\fR
.SS Colorizing a shaded relief map
Color can be added later
using \fIr.shade\fR
or \fId.shade\fR:
.br
.nf
\fC
r.shade shade=elevation_shade color=elevation output=elevation_shaded
\fR
.fi
.SS Using the scale factor in Latitude\-Longitude
In Latitude\-Longitude locations (or other non\-metric locations), the
\fIscale\fR factor has to be used:
.br
.nf
\fC
# Latitude\-Longitude example
g.region raster=srtm \-p
r.relief input=srtm output=srtm_shaded scale=111120
\fR
.fi
.SS Exporting shaded relief maps to GeoTIFF
The data range of shaded relief maps usually does not permit exporting the
map to GeoTIFF format along with its associated color table due to limitations
in the GeoTIFF format.
.PP
The most simple way to export it while even reducing the file size is
to export as palette byte map. This requires a conversion done
in \fIr.mapcalc\fR, using the #
operator to convert map category values to their grey scale
equivalents:
.br
.nf
\fC
# using the map created above
# create new map from map category values
r.mapcalc expression=\(dqelevation_shade_byte = #elevation_shade\(dq
# verify data range
r.info elevation_shade_byte
# assign grey color table
r.colors elevation_shade_byte color=grey
# export (optionally: createopt=\(dqCOMPRESS=DEFLATE,BIGTIFF=YES\(dq)
r.out.gdal input=elevation_shade_byte createopt=\(dqCOMPRESS=DEFLATE\(dq \(rs
           output=elevation_shade.tif
# add overview images in GeoTIFF file for faster zooming
gdaladdo \-\-config GDAL_CACHEMAX 2000 elevation_shade.tif 2 4 8 16
\fR
.fi
.SH SEE ALSO
.PP
\fI
d.shade,
d.his,
g.region,
r.shade,
r.blend,
r.colors,
r.mapcalc,
r.resamp.interp
\fR
.SH AUTHORS
Jim Westervelt, U.S. Army Construction Engineering Research Laboratory
.br
Markus Metz: Enhanced fast C version of r.relief for GRASS GIS 7
.SH SOURCE CODE
.PP
Available at: r.relief source code (history)
.PP
Main index |
Raster index |
Topics index |
Keywords index |
Graphical index |
Full index
.PP
© 2003\-2020
GRASS Development Team,
GRASS GIS 7.8.5 Reference Manual