[geos-devel] Is empty LinearRing closed?

[strk at refractions.net]

The only valid EMPTY geometry would be a GEOMETRYCOLLECTION.
All other possibilities should be avoided IMO.

--strk;

On Thu, Mar 30, 2006 at 08:52:06AM -0800, Martin Davis wrote:
> But the definition of LinearRing is that the start point equals the end point.   This makes the test unnecessary for a valid LinearRing.  However, maybe it's more general to use the explicit test.
> 
> As for an empty LinearRing, well, I don't know of any semantics which covers this.  This might be an angels-on-the-head-of-a-pin kind of thing.  If you don't like the JTS semantics for your particular use-case, you should just implement your own test.
> 
> Martin Davis, Senior Technical Architect
> Vivid Solutions Inc.      www.vividsolutions.com
> Suite #1A-2328 Government Street Victoria, B.C. V8T 5G5
> Phone: (250) 385 6040 - Local 308 Fax: (250) 385 6046
> 
> 
> > -----Original Message-----
> > From: geos-devel-bounces at geos.refractions.net 
> > [mailto:geos-devel-bounces at geos.refractions.net] On Behalf Of 
> > Mateusz Loskot
> > Sent: March 30, 2006 6:25 AM
> > To: GEOS Development List
> > Subject: [geos-devel] Is empty LinearRing closed?
> > 
> > 
> > Hi,
> > 
> > As I see, LinearRing is always closed:
> > 
> > bool LinearRing::isClosed() const {
> > 	return true;
> > }
> > 
> > GeometryFactory ::createLinearRing() call creates empty 
> > LinerRing. So, should it be considered as closed by default?
> > 
> > IMO empty LinearRing should not be considered as closed. OGC 
> > Simple Feature Spec. says about IsClosed for Curve type (base 
> > of LinearRing):
> > 
> > IsClosed( ):
> > (TRUE) if this Curve is closed (StartPoint ( ) = EndPoint ( )).
> > 
> > 
> > So, according to OGC SF Spec. LinearRing::isClosed() should 
> > be implemented as follows;
> > 
> > bool LinearRing::isClosed() const {
> > 	return (getStartPoint() == getEndPoint());
> > }
> > 
> > Am I correct?
> > 
> > Cheers
> > -- 
> > Mateusz £oskot
> > http://mateusz.loskot.net 
> > _______________________________________________
> > geos-devel mailing list
> > geos-devel at geos.refractions.net 
> > http://geos.refractions.net/mailman/listinfo/geos-devel
> > 
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