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Re: [Geojson] Question regarding RFC 7946

Andrew Harvey <andrew@alantgeo.com.au> Tue, 13 March 2018 23:14 UTC

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From: Andrew Harvey <andrew@alantgeo.com.au>
To: Martin Daly <Martin.Daly@cadcorp.com>, geojson@ietf.org
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Date: Wed, 14 Mar 2018 10:14:22 +1100
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Subject: Re: [Geojson] Question regarding RFC 7946
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Thank you Martin for clarifying this.


On Tue, 13 Mar 2018, at 12:20 AM, Martin Daly wrote:
> Andrew,


>  


> This is for consistency with OGC Simple Features which expects 1
> exterior + 0->N holes in a Polygon.>  


> The geometry you describe is represented as a MultiPolygon in SF. See
> Figure 17 in the standard:
> http://portal.opengeospatial.org/files/?artifact_id=25355>  


> Implementations may choose to be more flexible, of course.


>  


> Martin


>  


>  


> *From:* GeoJSON <geojson-bounces@ietf.org> *On Behalf Of *Andrew
> Harvey *Sent:* 12 March 2018 11:31 *To:* geojson@ietf.org *Subject:*
> [Geojson] Question regarding RFC 7946>  


> The spec says:


>  


>> For Polygons with more than one of these rings, the first MUST be the
>> exterior ring, and any others MUST be interior rings. The exterior
>> ring bounds the surface, and the interior rings (if present) bound
>> holes within the surface>  


> So does that mean that a Polygon geometry which has two interior rings
> where one falls inside another shouldn't create an island within a
> hole rather the smaller interior ring contained by the larger one
> becomes nullified?>  


> That is, the rendering we see at
> https://gist.github.com/andrewharvey/c092a6c4932a4d94ecb6cd59dc935b90
> is wrong and it shouldn't show an island in the middle?>  


> This arose when thinking about
> https://github.com/Turfjs/turf/issues/1305>  


> Many thanks,


> --


> Andrew Harvey


> CEO


> *Alantgeo*


>  


> www.alantgeo.com.au


> https://au.linkedin.com/in/andrewharveyau


> @alantgeo[1]


>  




Links:

  1. https://twitter.com/alantgeo

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