Difference between light-weight geometry types

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Difference between light-weight geometry types

Igor Stassiy
Hello,

is there any difference between LWCOLLECTION and LWCOMPOUND? Has the meaning changed since postgis 1.5 (when liblwgeom wasn't yet packaged) to liblwgeom >= 2.0? 

Also, what does LWCIRCSTRING stand for? Is it a closed line string?

Thanks a lot,
Igor

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Re: Difference between light-weight geometry types

Paul Ramsey
Yes, there's a difference.

A collection  (LWCOLLECTION) is just a bag'o'objects.
A compound curve (LWCOMPOUND) is a specific kind of linear object, one
defined by a set of linear primitives: LWLINE, a linear primitive made
by making linear interpolations between pairs of control vertices;
LWCIRCSTRING, a linear primitive made by making circular arc
interpolations between triples of control vertices. While a
LWCOLLECTION imposes no restrictions on its members, a LWCOMPOUND
expects its members to (a) be linear primitives (b) join up end-to-end
into a single linear object.

p.


On Mon, Mar 23, 2015 at 7:16 AM, Igor Stassiy <[hidden email]> wrote:

> Hello,
>
> is there any difference between LWCOLLECTION and LWCOMPOUND? Has the meaning
> changed since postgis 1.5 (when liblwgeom wasn't yet packaged) to liblwgeom
>>= 2.0?
>
> Also, what does LWCIRCSTRING stand for? Is it a closed line string?
>
> Thanks a lot,
> Igor
>
> _______________________________________________
> postgis-users mailing list
> [hidden email]
> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
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