<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>GRASS GIS: r.buffer</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.buffer</b></em> - Creates a raster map layer showing buffer zones surrounding cells that contain non-NULL category values. <h2>KEYWORDS</h2> raster, buffer <h2>SYNOPSIS</h2> <b>r.buffer</b><br> <b>r.buffer help</b><br> <b>r.buffer</b> [-<b>zq</b>] <b>input</b>=<em>name</em> <b>output</b>=<em>name</em> <b>distances</b>=<em>float</em>[,<i>float</i>,...] [<b>units</b>=<em>string</em>] [--<b>overwrite</b>] [--<b>verbose</b>] [--<b>quiet</b>] <h3>Flags:</h3> <DL> <DT><b>-z</b></DT> <DD>Ignore zero (0) data cells instead of NULL cells</DD> <DT><b>-q</b></DT> <DD>Run quietly</DD> <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>input</b>=<em>name</em></DT> <DD>Name of input raster map</DD> <DT><b>output</b>=<em>name</em></DT> <DD>Name for output raster map</DD> <DT><b>distances</b>=<em>float[,<i>float</i>,...]</em></DT> <DD>Distance zone(s)</DD> <DT><b>units</b>=<em>string</em></DT> <DD>Units of distance</DD> <DD>Options: <em>meters,kilometers,feet,miles,nautmiles</em></DD> <DD>Default: <em>meters</em></DD> </DL> <H2>DESCRIPTION</H2> <EM>r.buffer</EM> creates a new raster map layer showing buffer (a.k.a. "distance" or "proximity") zones around all cells that contain non-NULL category values in an existing raster map layer. The distances of buffer zones from cells with non-zero category values are user-chosen. Suppose, for example, that you want to place buffer zones around roads. This program could create the raster map layer shown below on the right based on road information contained in the raster map layer shown on the left. <div class="code"><pre> 000000000000000000000000 222233333333333333444444 111000000000000000000000 111222222222223333333333 000111111111100000000000 222111111111122223333333 000000001000011100000000 332222221222211122222222 000000001000000011111111 333333321233222211111111 000000001000000000000000 433333321233333222222222 000000001000000000000000 444443321233333333333333 000000001000000000000000 444443321233443333333333 000000001000000000000000 444443321233444444444444 Category 0: No roads Category 1: Road location Category 2: Buffer Zone 1 around roads Category 3: Buffer Zone 2 around roads Category 4: Buffer Zone 3 around roads </pre></div> <BR> <H2>NOTES</H2> The user has the option of identifying up to 250 continuous zones. The zones are identified by specifying the upper limit of each desired zone (<EM>r.buffer</EM> assumes that <tt>0</tt> is the starting point). ("Continuous" is used in the sense that each category zone's lower value is the previous zone's upper value. The first buffer zone always has distance <tt>0</tt> as its lower bound.) Buffer distances can be specified using one of five units with the <EM> units</EM> parameter: <EM>meters, kilometers, feet, miles</EM>, and <EM>nautmiles</EM> (nautical miles). <P> <!-- ??? is this the real method used or some ancient option ??? --> Distances from cells containing the user-specified category values are calculated using the "fromcell" method. This method locates each cell that contains a category value from which distances are to be calculated, and draws the requested distance rings around them. This method works very fast when there are few cells containing the category values of interest, but works slowly when there are numerous cells containing the category values of interest spread throughout the area. <P> <EM>r.buffer</EM> measures distances from center of cell to center of cell using Euclidean distance measure for planimetric locations (like UTM) and using ellipsoidal geodesic distance measure for latitude/longitude locations. <P> <EM>r.buffer</EM> calculates distance zones from all cells having non-NULL category values in the <EM>input</EM> map. If the user wishes to calculate distances from only selected <EM>input</EM> map layer category values, the user should run (for example) <EM><A HREF="r.reclass.html">r.reclass</A></EM> prior to <EM>r.buffer</EM>, to reclass all categories from which distance zones are not desired to be calculated into category NULL. <P> The <B>-z</B> flag can be used to ignore raster values of zero instead of NULL values in the input raster map. <P> <H2>EXAMPLE</H2> In the following example, the buffer zones would be (in the default units of meters): 0-100, 101-200, 201-300, 301-400 and 401-500. <BR> <div class="code"><pre> <B>r.buffer input=</B>roads <B>output=</B>roads.buf <B>distances=</B>100,200,300,400,500 </pre></div> Result: <div class="code"><pre> <B>r.category input=</B>roads.buf 1 distances calculated from these locations 2 0-100 meters 3 100-200 meters 4 200-300 meters 5 300-400 meters 6 400-500 meters </pre></div> <H2>SEE ALSO</H2> <EM> <A HREF="g.region.html">g.region</A><br> <A HREF="r.cost.html">r.cost</A><br> <A HREF="r.mapcalc.html">r.mapcalc</A><br> <A HREF="r.reclass.html">r.reclass</A><br> <A HREF="v.buffer.html">v.buffer</A> </EM> <H2>AUTHORS</H2> Michael Shapiro, U.S. Army Construction Engineering Research Laboratory <BR> James Westervelt, U.S. Army Construction Engineering Research Laboratory <p> <i>Last changed: $Date: 2008-02-19 21:18:46 +0100 (Tue, 19 Feb 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>