[Gdal-dev] OGC Spec getExteriorRing() for a Polygon

[Chapman, Martin]

Frank,

Ok, I agree, I was just curious why you did that.  According to the OGC,
the only difference is a that a LinearRing is both closed and simple,
whereas a LineString does not need to be closed or simple.  According to
OGC a Polygon consists of a set of LinearRings that make up its exterior
and interior
boundaries.  Thus, sounds like the OGC docs are incorrect and have
conflicting definitions.  Shall I inform the OGC board that their spec
is not to spec?....HA, just kidding.
 
Martin

-----Original Message-----
From: Frank Warmerdam [mailto:warmerdam at pobox.com] 
Sent: Tuesday, July 20, 2004 4:08 PM
To: Chapman, Martin
Cc: gdal-dev at remotesensing.org
Subject: Re: [Gdal-dev] OGC Spec getExteriorRing() for a Polygon


Chapman, Martin wrote:
> Frank,
>  
> The OGC Spec says that the Polygon method getExteriorRing() should
> return a LineString.  Just out of curiosity, why do you return a 
> LinearRing from your implementation OGRPolygon::getExteriorRing()?  It

> would make sense to me that the spec is wrong and what you want is 
> always a ring.  Do you think the OGC spec is wrong.  The following is 
> from the spec:

Martin,

Since a linearring is a subclass of linestring, a linearring is
technically a linestring.  I don't know why the Simple Features for SQL
specifies line string.  It seems kind of brain dead, and not something
I'm going to change OGR to adhere to.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam,
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and watch the world go round - Rush    | Geospatial Programmer for Rent