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57 lines
2.9 KiB
HTML
57 lines
2.9 KiB
HTML
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<html>
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<head><link rel="stylesheet" type="text/css" href="help.css"/></head>
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<body>
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<h1 class='module'>Peuker Douglas</h1>
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<div class='author'>(c) 2010 by David G. Tarboton</div>
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<div class='description'>Creates an indicator grid (1, 0) of upward curved
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grid cells according to the Peuker and Douglas algorithm.</div>
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<div class='description'>With this tool, the DEM is first smoothed by a
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kernel with weights at the center, sides, and diagonals. The Peuker and
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Douglas (1975) method (also explained in Band, 1986), is then used to
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identify upwardly curving grid cells. This technique flags the entire grid,
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then examines in a single pass each quadrant of 4 grid cells, and unflags
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the highest. The remaining flagged cells are deemed "upwardly curved",
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and when viewed, resemble a channel network. This proto-channel network
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generally lacks connectivity and requires thinning, issues that were
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discussed in detail by Band (1986).</div>
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<ol>
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<li>Band, L. E., (1986), "Topographic partition of watersheds with
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digital elevation models", Water Resources Research, 22(1): 15-24.</li>
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<li>Peuker, T. K. and D. H. Douglas, (1975), "Detection of surface-specific
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points by local parallel processing of discrete terrain elevation data",
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Comput. Graphics Image Process., 4: 375-387.</li>
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</ol>
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<h2>Parameters</h2>
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<dl class='parameters'>
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<dt>Number of Processes <div class='type'>Integer</div></dt>
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<dd>The number of stripes that the domain will be divided into and the
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number of MPI parallel processes that will be spawned to evaluate each
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of the stripes.</dd>
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<dt>Elevation Grid <div class='type'>Raster Grid</div></dt>
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<dd>A grid of elevation values. This is usually the output of the "Pit
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Remove" tool, in which case it is elevations with pits removed.</dd>
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<dt>Center Smoothing Weight <div class='type'>Double</div></dt>
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<dd>The center weight parameter used by a kernel to smooth the DEM
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before the tool identifies upwardly curved grid cells. Default value
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is <strong>0.4</strong>.</dd>
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<dt>Side Smoothing Weight <div class='type'>Double</div></dt>
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<dd>The side weight parameter used by a kernel to smooth the DEM before
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the tool identifies upwardly curved grid cells. Default value is
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<strong>0.1</strong>.</dd>
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<dt>Diagonal Smoothing Weight <div class='type'>Double</div></dt>
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<dd>The diagonal weight parameter used by a kernel to smooth the DEM
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before the tool identifies upwardly curved grid cells. Default value
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is <strong>0.05</strong>.</dd>
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</dl>
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<h2>Outputs</h2>
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<dl class='parameters'>
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<dt>Stream Source Grid <div class='type'>Raster Grid</div></dt>
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<dd>An indicator grid (1, 0) of upward curved grid cells according to
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the Peuker and Douglas algorithm, and if viewed, resembles a channel
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network. This proto-channel network generally lacks connectivity and
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requires thinning, issues that were discussed in detail by Band (1986).</dd>
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</dl>
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</body></html>
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