[postgis-users] PostGIS geography question: wrapping the globe

[Paul Ramsey]

If you can stand it, go slightly smaller than -90,90. do -89,89. That
way the chords are < 180 degrees and go in the directions you expect.

Or, build your box of smaller chords, so go from -90 to -45 to 0 to 45
to 90. That will work too.

The basic rule is: given two points in geography space, which
(naturally) define a great circle, the arc they define is the smaller
of the two arcs in the circle.

P.

On Mon, Jun 14, 2010 at 10:05 PM,  <pcreso at pcreso.com> wrote:
>
> This is also an issue for geometries, but I'm looking for a geography solution here.
>
> How can I create a geography that goes from -90 to 90 & crosses the dateline vs one that goes the other way around the globe & crosses the 0 degree meridian?
>
> Either/both is defined by:
>
> POLYGON((-90 10, -90 -10, 90 -10, -90 -10, -90 10))
>
> How can I tell which one I'll get (apart from trying it out) & how do I get the other, if that is what I want?
>
> I assume I can use intermediate points along the lines to coerce the direction I want, but this has some problems in my use case.
>
> Thanks,
>
>  Brent
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