<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>GRASS GIS: r.shaded.relief</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <link rel="stylesheet" href="grassdocs.css" type="text/css"> </head> <body bgcolor="white"> <img src="grass_logo.png" alt="GRASS logo"><hr align=center size=6 noshade> <h2>NAME</h2> <em><b>r.shaded.relief</b></em> - Creates shaded relief map from an elevation map (DEM). <h2>KEYWORDS</h2> raster, elevation <h2>SYNOPSIS</h2> <b>r.shaded.relief</b><br> <b>r.shaded.relief help</b><br> <b>r.shaded.relief</b> <b>map</b>=<em>string</em> [<b>shadedmap</b>=<em>string</em>] [<b>altitude</b>=<em>integer</em>] [<b>azimuth</b>=<em>integer</em>] [<b>zmult</b>=<em>float</em>] [<b>scale</b>=<em>float</em>] [<b>units</b>=<em>string</em>] [--<b>overwrite</b>] [--<b>verbose</b>] [--<b>quiet</b>] <h3>Flags:</h3> <DL> <DT><b>--overwrite</b></DT> <DD>Allow output files to overwrite existing files</DD> <DT><b>--verbose</b></DT> <DD>Verbose module output</DD> <DT><b>--quiet</b></DT> <DD>Quiet module output</DD> </DL> <h3>Parameters:</h3> <DL> <DT><b>map</b>=<em>string</em></DT> <DD>Input elevation map</DD> <DT><b>shadedmap</b>=<em>string</em></DT> <DD>Output shaded relief map name</DD> <DT><b>altitude</b>=<em>integer</em></DT> <DD>Altitude of the sun in degrees above the horizon</DD> <DD>Options: <em>0-90</em></DD> <DD>Default: <em>30</em></DD> <DT><b>azimuth</b>=<em>integer</em></DT> <DD>Azimuth of the sun in degrees to the east of north</DD> <DD>Options: <em>0-360</em></DD> <DD>Default: <em>270</em></DD> <DT><b>zmult</b>=<em>float</em></DT> <DD>Factor for exaggerating relief</DD> <DD>Default: <em>1</em></DD> <DT><b>scale</b>=<em>float</em></DT> <DD>Scale factor for converting horizontal units to elevation units</DD> <DD>Default: <em>1</em></DD> <DT><b>units</b>=<em>string</em></DT> <DD>Set scaling factor (applies to lat./long. locations only)</DD> <DD>Options: <em>meters,feet</em></DD> </DL> <H2>DESCRIPTION</H2> <EM>r.shaded.relief</EM> is a Bourne shell script that 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 <EM><input_map>.shade</EM>. The map is assigned a grey-scale color table. <P> If no parameters are provided on startup, this program is interactive; thus if the user enters the command: <DL> <DD> <B>r.shaded.relief</B> </DL> The program then prompts the user to enter values for: <OL> <LI>The <B>altitude</B> of the sun in degrees above the horizon (a value between 0 and 90 degrees), and <LI>The <B>azimuth</B> of the sun in degrees to the east of north (a value between 0 and 360 degrees). <LI>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. <LI>The scaling parameter, which compensates for a different horizontal <B>scale</B> 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.) <br>For ETOPO2 data a scale factor of 10000 generates an acceptable shading effect. <LI>For the special case when a latitude-longitude projection is used with an elevation map measured in meters or feet, the <B>units</B> can be set to automatically set the horizontal scale to the the number of meters or feet 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. <LI>The <b>zmult</b> 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) </OL> Specifically, <EM>r.shaded.relief</EM> executes a <EM><A HREF="r.mapcalc.html">r.mapcalc</A></EM> statement. Refer to the manual entry for <EM><A HREF="r.mapcalc.html">r.mapcalc</A></EM> for an explanation of the filtering syntax shown in the above expression. See, for example, the section on "The Neighborhood Modifier". <P> <EM>r.shaded.relief</EM> then runs <EM><a href="r.colors.html">r.colors</A></EM> to assign a grey-scale color table to the new shaded relief map. <H2>NOTES</H2> To visually improve the result of shade maps from low resolution elevation models, use <em>r.resamp.interp</em> with bilinear or bicubic method to resample the DEM at higher resolution. <EM>r.shaded.relief</EM> is then run on the resampled DEM. <H2>FILES</H2> This program is simply a shell script. Users are encouraged to make their own shell scripts using similar techniques. See <KBD>$GISBASE/scripts/r.shaded.relief</KBD>. <H2>SEE ALSO</H2> <i>An Algebra for GIS and Image Processing</i>, by Michael Shapiro and Jim Westervelt, U.S. Army Construction Engineering Research Laboratory (March/1991) (get from GRASS web site). <P> <!-- RGB version not ported to GRASS 6: <EM><A HREF="shade.clr.sh.html">shade.clr.sh</A></EM><BR> --> <EM> <A HREF="d.his.html">d.his</A>,<br> <A HREF="g.region.html">g.region</A>,<br> <A HREF="r.blend.html">r.blend</A>,<br> <A HREF="r.colors.html">r.colors</A>,<br> <A HREF="r.mapcalc.html">r.mapcalc</A>,<br> <A HREF="r.resamp.interp.html">r.resamp.interp</A> </EM> <H2>AUTHOR</H2> Jim Westervelt, U.S. Army Construction Engineering Research Laboratory <p><i>Last changed: $Date: 2008-03-26 15:02:09 +0100 (Wed, 26 Mar 2008) $</i> <HR> <P><a href="index.html">Main index</a> - <a href="raster.html">raster index</a> - <a href="full_index.html">Full index</a></P> <P>© 2003-2008 <a href="http://grass.osgeo.org">GRASS Development Team</a></p> </body> </html>
