[gdal-dev] Time for a new GeoJSON driver?

[Sean Gillies]

On Mon, Jul 25, 2016 at 5:24 PM, Jukka Rahkonen <
jukka.rahkonen at maanmittauslaitos.fi> wrote:

> Even Rouault <even.rouault <at> spatialys.com> writes:
>
>
> > - right hand rule of polygons
>
> Which means actually left hand rule if I have understood the right
> hand/left
> hand rules correctly. If you walk along the polygon rings the name of the
> rule is telling where the interior of the polygon is. If you follow the
> outer ring that is winding counterclockwise the interior in on your left
> hand side.
>
> I may be wrong. And the rule does not explicitly say anything about people
> walking backwards.
>

This is the reference for the right-hand rule:

  https://en.wikipedia.org/wiki/Right-hand_rule

A polygon patch with a positive area has a normal vector pointing "up",
away from the center of the earth. Point your thumb of your right hand in
the same direction and the curl of your fingers indicates the winding order
of the polygon vertices.

OGC 06-142r1 "GML 3.1.1 PIDF-LO Shape Application Schema for use by the
Internet Engineering Task Force (IETF)" uses the same right-hand rule as
GeoJSON.

-- 
Sean Gillies
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