<div>Hi Micha,</div>
<div> </div>
<div>May be with <strong>r.neighbors </strong>combined with <em>interspersion</em> method you can solve this.</div>
<div> </div>
<div>good luck</div>
<div> </div>
<div>milton</div>
<div>brazil=toronto<br><br></div>
<div class="gmail_quote">2009/8/2 Micha Silver <span dir="ltr"><<a href="mailto:micha@arava.co.il">micha@arava.co.il</a>></span><br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">How can I avoid the problem of strings of single cells when creating basins with r.watershed? I think this is referred to as "ladders". Here's [1] an image showing what I mean.<br>
<br>In my example, the purple colored catchment has two "tails" of width 1 cell. One tail separates between the light green and the pale blue catchments. The other (northern) tail splits the dark green catchment into two.<br>
<br>After running r.to.vect to get the catchment vectors, I'm left with the two "strings" or "ladders" of tiny vector areas. The southern string can be removed with v.clean tool=rmarea with no ill effects.<br>
<br>However when I remove those small areas in the northern "ladder" I'm left with the stream running *along the drainage divide* or even zigzagging across the divide, neither of which is correct.<br><br>Can this problem be avoided? I've tried with a couple of different dem sources, and at different resolutions and threshold values, but these ladder phenomena always seem to appear.<br>
<br>This example was done with the ASTER DEM data, using a threshold of 11000 and resolution like the original data (1 arcsec ~= 30 m.)<br><br><br>Thanks,<br><br>Micha<br><br><br>[1] <a href="http://my.arava.co.il/~micha/ladders.html" target="_blank">http://my.arava.co.il/~micha/ladders.html</a><br>
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