Its one of those frustrating things I guess where I visually plot, yet can't figure out how to program :(. Well maybe some day.
-----Original Message----- From: [EMAIL PROTECTED] on behalf of Martin Davis Sent: Mon 11/24/2008 2:37 PM To: PostGIS Users Discussion Subject: Re: [postgis-users] Get concave hull from an array oflongitude inlatitude points Yeah, I saw that too. Unfortunately the algorithm is only available by email, and is implemented in Mathematica. It also sounds somewhat complex. But I guess this sort of answers my question - there are algorithms which people have called "concave hull", and they produce concave polygons from sets of points in some kind of way. I don't think there's any consensus on what algorithm to use, though. One interesting approach is here: http://grass.osgeo.org/wiki/Create_concave_hull In any case, obviously this isn't in PostGIS right now. Obe, Regina wrote: > > Evidentally its this thing > http://ubicomp.algoritmi.uminho.pt/local/concavehull.html > > So I guess basically you take the boundary and you get rid of points > that have points sitting to the right/left/top/or bottom of it and then > you form a polygon from the remaining points. > > Well at least that is what it seems like to me visually. Just not > quite sure how to program such a thing without writing yuck procedural > code. > > Hope that helps, > Regina > > > -----Original Message----- > From: [EMAIL PROTECTED] on behalf of > Martin Davis > Sent: Mon 11/24/2008 1:58 PM > To: PostGIS Users Discussion > Subject: Re: [postgis-users] Get concave hull from an array of > longitude inlatitude points > > What's a concave hull? > > Ales Kecman wrote: > > Hi! > > > > > > I'm new to Postgis and would really like to get some help on getting a > > concave hull from an array of points. > > > > For example: > > > > I have an array of points - longitude and latitude of buildings in > > particular area in the city. I already managed to get a convex hull > > polygon from this array of points, but this is not really helpful. > > What I'm trying to get is some kind of concave hull polygon from an > > array of points, which I would further like to use in Google Earth kml > > file. > > > > Thanks. > > ------------------------------------------------------------------------ > > > > _______________________________________________ > > postgis-users mailing list > > postgis-users@postgis.refractions.net > > http://postgis.refractions.net/mailman/listinfo/postgis-users > > > > -- > Martin Davis > Senior Technical Architect > Refractions Research, Inc. > (250) 383-3022 > > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users > > ------------------------------------------------------------------------ > > *The substance of this message, including any attachments, may be > confidential, legally privileged and/or exempt from disclosure > pursuant to Massachusetts law. It is intended solely for the > addressee. If you received this in error, please contact the sender > and delete the material from any computer. * > > ------------------------------------------------------------------------ > > * Help make the earth a greener place. If at all possible resist > printing this email and join us in saving paper. * > > * * > > * * > > ------------------------------------------------------------------------ > > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users > -- Martin Davis Senior Technical Architect Refractions Research, Inc. (250) 383-3022 _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
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