[postgis-users] ST_Boundary of some linestrings

[Stephen Woodbridge]

lisek lichu wrote:
> Hello,
> 
> I hane in my database 6 linestrings and I want to get the boundary 
> rectangle from them (not from each of them)
> 
> If i use:
> select AsText(ST_Boundary(the_geom)) from segments;
> 
> i get
> 
> MULTIPOINT(-8.593025208 41.180818082,-8.594827652 41.187632944)
> MULTIPOINT(-8.594827652 41.187632944,-8.591823578 41.193090782)
> MULTIPOINT(-8.591823578 41.193090782,-8.611950874 41.190119708)
> MULTIPOINT(-8.611950874 41.190119708,-8.613796234 41.179203081)
> MULTIPOINT(-8.613796234 41.179203081,-8.602809906 41.180559684)
> MULTIPOINT(-8.602809906 41.180559684,-8.593025208 41.180818082)
> 
> 
> but i need one big Boundary. (should I group them by some atribute or 
> there is some siplier way to do that?)

select AsText(ST_Envelope(ST_Collect(the_geom))) from segments;

Does this work for you?

-Steve