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<em>r.li.patchdensity</em> calculates the "patch density index",
4
the number of patches per square kilometer, as:
5
<div class="code"><pre>
11
<li><b>A</b>:sampling area size</li>
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<li><b>Npatch</b>: number of patches</li>
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This index is calculated using a 4 neighbour algorithm, diagonal cells
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are ignored when tracing a patch.
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Do not use absolute path names for the <b>config</b> and <b>output</b>
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If the "moving window" method was selected in <b>g.gui.rlisetup</b>, then the
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output will be a raster map, otherwise an ASCII file will be generated in
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the folder <tt>C:\Users\userxy\AppData\Roaming\GRASS7\r.li\output\</tt>
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(MS-Windows) or <tt>$HOME/.grass7/r.li/output/</tt> (GNU/Linux).
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A sample area of only NULL values is considered to have zero patches,
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that is, the result is always ≥ 0.
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To calculate patch density index on map <em>my_map</em>, using
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<em>my_conf</em> configuration file (previously defined with
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<em>g.gui.rlisetup</em>) and saving results in <em>my_out</em>, run:
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<div class="code"><pre>
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r.li.patchdensity input=my_map conf=my_conf output=my_out
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Example for Spearfish forest areas:
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<div class="code"><pre>
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g.region raster=landcover.30m -p
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# extract forested areas:
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r.category landcover.30m
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r.mapcalc "forests = if(landcover.30m >= 41 && landcover.30m <= 43, 1, null())"
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# patch density (7x7 moving window defined in g.gui.rlisetup):
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r.li.patchdensity forests conf=movwindow7 out=forests_p_dens7
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r.univar forests_p_dens7
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d.rast.leg forests_p_dens7
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r.to.vect forests out=forests feature=area
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d.vect forests type=boundary
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Forest map (North Carolina sample dataset) example:
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<div class="code"><pre>
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g.region raster=landclass96 -p
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r.mapcalc "forests = if(landclass96 == 5, 1, null() )"
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r.li.patchdensity input=forests conf=movwindow7 out=forests_patchdensity_mov7
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r.univar forests_patchdensity_mov7
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r.to.vect input=forests output=forests type=area
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d.rast forests_patchdensity_mov7
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d.vect forests type=boundary
74
<a href="r.li.html">r.li</a> - package overview<br>
75
<a href="g.gui.rlisetup.html">g.gui.rlisetup</a>
79
McGarigal, K., and B. J. Marks. 1995. FRAGSTATS: spatial pattern
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analysis program for quantifying landscape structure. USDA For. Serv.
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Gen. Tech. Rep. PNW-351. (<a href="http://treesearch.fs.fed.us/pubs/3064">PDF</a>)
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Michael Shapiro - CERL (patch identification)<br>
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Markus Metz (statistics)
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<i>Last changed: $Date: 2014-12-19 22:55:37 +0100 (Fri, 19 Dec 2014) $</i>