DESCRIPTION
r.shaded.relief 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 <input_map
>.shade. The map is assigned a grey-scale color table.
The parameters controlling the shading are:
- 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.
- The altitude of the sun in degrees above the horizon
(a value between 0 and 90 degrees).
- The azimuth of the sun in degrees to the east of north
(a value between 0 and 360 degrees).
- The scaling parameter, which compensates for a different
horizontal scale 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.)
- The zmult 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)
- Horizontal distances are calculated in meters, using geodesic
distances for a latitude-longitude projection. With an elevation map
measured in feet, the units 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 units parameter overrides
the scale parameter.
r.shaded.relief assigns a grey-scale color table to the new
shaded relief map.
NOTES
To visually improve the result of shade maps from low resolution elevation
models, use r.resamp.interp with bilinear or bicubic method to
resample the DEM at higher resolution. r.shaded.relief is then
run on the resampled DEM.
EXAMPLES
In this example, the aspect map in the North Carolina sample
dataset location is used to hillshade the elevation map:
g.region rast=elevation -p
r.shaded.relief input=elevation output=elevation.shaded
In Latitude-Longitude locations (or other non-metric locations), the
scale factor has to be used:
# Latitude-Longitude example
r.shaded.relief input=srtm output=srtm.shaded scale=111120
SEE ALSO
d.his,
g.region,
r.blend,
r.colors,
r.mapcalc,
r.resamp.interp
AUTHORS
Jim Westervelt, U.S. Army Construction Engineering Research Laboratory
Markus Metz: GRASS GIS 7- enhanced fast C version of r.shaded.relief
Last changed: $Date$