I think perhaps st_buildarea and st_collect might be what you want. Below is what I used to create a hexagon out of points->lines which was then translated (using generate_series) across X and Y to create a hexagonal grid for the County. There's probably a simpler way to make a hexagon but it illustrates the st_buildarea. Maybe that helps. -Eric --let's make a hexagon with 1000 foot sides and position it with it's --center at 1210000, 610000 (the lower left of the pamap tile extent for Erie County) --and create a table drop table if exists hex1000; create table hex1000 as select translate(st_buildarea(st_collect(geom)),1210000, 610000) as geom from (select makeline(st_endpoint(makeline(makepoint(0, 0),makepoint(0, - 1000))),st_endpoint(rotate(makeline(makepoint(0, 0),makepoint(0, -1000)), radians(300)))) as geom union select makeline(st_endpoint(rotate(makeline(makepoint(0, 0),makepoint(0, -1000)), radians(300))),st_endpoint(rotate(makeline(makepoint(0, 0),makepoint(0, -1000)), radians(240)))) as geom union select makeline(st_endpoint(rotate(makeline(makepoint(0, 0),makepoint(0, -1000)), radians(240))),st_endpoint(rotate(makeline(makepoint(0, 0),makepoint(0, -1000)), radians(180)))) as geom union select makeline(st_endpoint(rotate(makeline(makepoint(0, 0),makepoint(0, -1000)), radians(180))),st_endpoint(rotate(makeline(makepoint(0, 0),makepoint(0, -1000)), radians(120)))) as geom union select makeline(st_endpoint(rotate(makeline(makepoint(0, 0),makepoint(0, -1000)), radians(120))),st_endpoint(rotate(makeline(makepoint(0, 0),makepoint(0, -1000)), radians(60)))) as geom union select makeline(st_endpoint(rotate(makeline(makepoint(0, 0),makepoint(0, -1000)), radians(60))),st_endpoint(rotate(makeline(makepoint(0, 0),makepoint(0, -1000)), radians(0)))) as geom ) as t1;
-----Original Message----- From: [email protected] [mailto:[email protected]]on Behalf Of Avery Penniston Sent: Tuesday, June 22, 2010 2:38 PM To: [email protected] Subject: Re: [postgis-users] Create POLYGON from Several LINESTRINGs I'm trying to create 'pie wedge' shaped polygons by building them in a Postgres function. I am able to create the 2 straight chords and the arc as separate LINESTRINGs, and I have verified that each LINESTRING shares its endpoints with the other two LINESTRINGs. However, I am having trouble putting the individual parts together to form a POLYGON. I tried to ST_UNION the 3 LINESTRINGs together, and the result is a MULTILINESTRING. I then call ST_LINEMERGE to convert the MULTILINESTRING to a single LINESTRING so I can pass it to the ST_POLYGON function, but the result of the ST_LINEMERGE is a MULTILINESTRING. I tried using ST_COLLECT instead of ST_UNION, but then I got a GEOMETRYCOLLECTION containing a MULTILINESTRING and a LINESTRING. Does anybody have some advice for creating a POLYGON from 3 or more separate LINESTRINGs?
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