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Re: [Geojson] Question regarding RFC 7946

Martin Daly <Martin.Daly@cadcorp.com> Mon, 12 March 2018 13:19 UTC

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From: Martin Daly <Martin.Daly@cadcorp.com>
To: 'Andrew Harvey' <andrew@alantgeo.com.au>, "geojson@ietf.org" <geojson@ietf.org>
Thread-Topic: [Geojson] Question regarding RFC 7946
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Date: Mon, 12 Mar 2018 13:20:04 +0000
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Subject: Re: [Geojson] Question regarding RFC 7946
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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<http://www.alantgeo.com.au>
https://au.linkedin.com/in/andrewharveyau
@alantgeo<https://twitter.com/alantgeo>

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