I hope you'll tell us your final choice ! In your last query you need to add a pair of bracket to get only geometries from dump. Syntax is : (st_dump(geom)).geom.
Hug Tom McCallum <[email protected]> a écrit : Thanks for all your replies, not quite there but got some ideas. On Mon, 27 Jan 2014 13:51:26 -0000, Rémi Cura <[email protected]> wrote: > You could use convex or concav envelop. > You can also union the geometries (eventually simplifying by neg buffer > then pos buffer) > That's if you want precise boundary. > If you just need bbox ... > Cheers, > Rémi-C > > > 2014-01-27 Hugues François <[email protected]> > >> Hello, >> >> On my side, I often use >> st_buildarea(st_exteriorring((st_dump(geom)).geom)). And if I want to >> keep >> a single object for the original one, I union or collect them regarding >> their gid. >> >> HTH >> >> Hugues. >> >> >> >> >> -----Original Message----- >> From: [email protected] [mailto: >> [email protected]] On Behalf Of Tom McCallum >> Sent: Monday, January 27, 2014 1:51 PM >> To: PostGIS Users Discussion >> Subject: Re: [postgis-users] Getting boundary of set of polygons >> >> St_MakePolygon does not take a multilinestring. >> ST_BuildArea looked possible, but it gives me back lots of little areas >> and not a single boundary for the whole set. >> >> It looks as though ST_Dump with ST_MakePolygon may be useful but am >> still >> trying to get the right form something like >> >> ST_MakePolygon( ST_DUMP( ST_BOUNDARY( ST_COLLECT( wkb_boundary ) ) >> .geom ) >> >> But it does not like the .geom bit. >> >> Any suggestions? >> >> On Mon, 27 Jan 2014 12:35:51 -0000, Nicolas Ribot >> <[email protected]> >> wrote: >> >> > Hi, >> > >> > You should try st_makePolygon, or st_buildArea depending on the result >> > you want (keeping holes or removing them). >> > >> > Nicolas >> > >> > >> > >> > On 27 January 2014 13:32, Tom McCallum <[email protected]> wrote: >> > >> >> Hello all, >> >> >> >> I am trying to get the boundary of a geometry(polygon) field in >> >> postgis (multiple polygons in this field). I have this so far: >> >> >> >> ST_BOUNDARY(ST_COLLECT(wkb_geometry)) >> >> >> >> which outputs MultilineString. I need to convert this to a polygon. >> >> I have tried all sorts of things from ST_DUMP to converting to text >> >> and then trying ST_BdPolyFromText but got nothing to work so far. >> >> ST_Convexhull gives me a polygon but unfortunately its not what I >> >> want. >> >> >> >> Could someone let me know what I should be calling. >> >> >> >> Thanks >> >> >> >> Tom >> >> _______________________________________________ >> >> postgis-users mailing list >> >> [email protected] >> >> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list [email protected] http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list [email protected] http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
