[postgis-users] Create POLYGON from Several LINESTRINGs

[Avery Penniston]

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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