[Geojson] polygon point order

[Paul Ramsey]

The same thing applies to linestrings...

Does ( [100,0], [-90,0] ) to over the dateline or over greenwich?

I think the "law of the minimum" is a workable compromise, which says to 
always take the smaller interpretation (the one < 180 degrees wide).  In 
exchange for that maximum size interpretation, you can ignore ordering, 
and the rule works for any line, not just closed polygons, the way 
clockwise/anti-clockwise does.

P.

Keith Jenkins wrote:
> Thanks to everyone for all the work going into the GeoJSON draft.
> I've only now read it through in its entirety, and have a question
> about polygon point order.  (this is different from the
> recently-discussed lon/lat order)
> 
> Q: Should the point order of polygons be specified to be either
> clockwise or counterclockwise?
> 
> Without a defined direction, a polygon like [ [-90,0], [90,0],
> [90,20], [-90,20], [-90, 0] ] is ambiguous -- it could cross either
> the Atlantic or the Pacific.
> 
> Some confounding issues:
> * Some client interfaces scroll across longitude 180, but others don't.
> * A user might define a new polygon in either direction (although the
> client could reverse the sequence as necessary before sending to the
> server).
> * Most polygons are not anywhere near 180 degrees wide, so a client
> could safely assume the smaller of the two options in most cases.
> 
> I had a similar question about the point order for bounding boxes that
> cross longitude 180, but it sounds like the box is being dropped from
> GeoJSON.
> 
> Keith
> 
> p.s. I didn't find any prior discussion on the list archive, so
> forgive me if this has already been hashed out.
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   Paul Ramsey
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