https://grasswiki.osgeo.org/w/api.php?action=feedcontributions&feedformat=atom&user=%E2%9A%A0%EF%B8%8FPhillipPlascencia 2026-05-26T08:25:59Z User contributions MediaWiki 1.41.0 https://grasswiki.osgeo.org/w/index.php?title=Create_concave_hull&diff=12154 2010-11-25T14:41:03Z

<p>⚠️PhillipPlascencia: </p> <hr /> <div>Q: I have a set of points and would like to compute the concave hull of it.<br /> <br /> A: You can approximate a concave hull through the following steps:<br /> <br /> * create map of lines connecting all points (I find it easier to do this with v.net.visibility, but v.distance works also)<br /> * add a table with a column 'cat' and a column 'length double precision' and categories to these lines (v.db.addtable, v.category)<br /> * upload the length of each line to the table (v.to.db)<br /> * visually identify a length threshold above which the lines should not be used<br /> * extract only those lines below that threshold (v.extract where=&quot;length&lt;MAXLENGTH)<br /> * convert the lines to boundaries (v.type)<br /> * break overlapping lines (v.clean tool=break, there shouldn't be any duplicate lines, but just in case you can also use rmdupl)<br /> * add centroids with the same category value to the boundaries (v.centroids step=0)<br /> * dissolve the areas into one (v.dissolve)<br /> <br /> The image to shows the results:<br /> <br /> [[Image:Concave_hull.jpg|500px]]<br /> <br /> <br /> [[Category:FAQ]]<br /> <br /> [http://www.thesiswritingservice.com/ thesis writing]</div>

⚠️PhillipPlascencia