Ubuntu Manpage: r.shaded.relief - Creates shaded relief map from an elevation map (DEM).

NAME

       r.shaded.relief  - Creates shaded relief map from an elevation map (DEM).

KEYWORDS

       raster, elevation

SYNOPSIS

       r.shaded.relief
       r.shaded.relief help
       r.shaded.relief   map=string   [shadedmap=string]    [altitude=float]    [azimuth=float]    [zmult=float]
       [scale=float]   [units=string]   [--overwrite]  [--verbose]  [--quiet]

   Flags:
       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       map=string
           Input elevation map

       shadedmap=string
           Output shaded relief map name

       altitude=float
           Altitude of the sun in degrees above the horizon
           Options: 0-90
           Default: 30

       azimuth=float
           Azimuth of the sun in degrees to the east of north
           Options: 0-360
           Default: 270

       zmult=float
           Factor for exaggerating relief
           Default: 1

       scale=float
           Scale factor for converting horizontal units to elevation units
           Default: 1

       units=string
           Set scaling factor (applies to lat./long. locations only, none: scale=1)
           Options: none,meters,feet
           Default: none

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 .shade. The map is assigned a grey-scale color table.

The module then prompts the user to enter values for:

1 The altitude of the sun in degrees above the horizon (a value between 0 and 90 degrees), and

2 The azimuth of the sun in degrees to the east of north (a value between 0 and 360 degrees).

3 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.

4 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.)

5 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 units 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
units parameter overrides the scale parameter.

6 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)

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.

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 map=elevation shadedmap=elevation.shaded

       In Latitude-Longitude locations (or other non-metric locations), the scale factor has to be used:
       # Latitude-Longitude example
       r.shaded.relief map=srtm shadedmap=srtm.shaded scale=111120

AUTHOR

       Jim Westervelt, U.S. Army Construction Engineering Research Laboratory

       Last changed: $Date: 2011-11-08 03:29:50 -0800 (Tue, 08 Nov 2011) $

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