[postgis-users] Display GEOGRAPHY polygons crossing date line

[iam_gilbey]

I have many polygons, including several that cross the date line. They are
stored as GEOGRAPHY and work perfectly with PostGIS v2.0.1, PostgreSQL 9.1.3
on windows XP. I can serve this data using Geoserver (v2.1), and view it
using open layers, where the polygons crossing the date line render
correctly.

I cannot however convert the data into KML (viewed in Google Earth 5.1), or
view it in Quantum GIS (v1.7), without the date line polygons being wrapped
around the earth.

I appreciate that this isn't strictly a postGIS problem, however being faced
with the stark choice between splitting my data about the date line
(inelegant) or not using Google Earth (unacceptable to users), I don't know
where else to turn!

Do you know of:
a) a way to get the data to render correctly in Google Earth; or
b) where else I should ask?

Thanks!



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[Paul Ramsey]

Even if you split the shapes, GEarth renders polygons in a non-normal
kind of way which you might find unacceptable

http://blog.opengeo.org/2010/08/10/shape-of-a-polygon/

The quick fix is to render them as lines, not polygons. there's no fix
to get them to fill using great circle edges, GEarth just doesn't work
that way.

P.

[iam_gilbey]

Thanks for that info - it's something else to consider.

Conclusion: Google Earth cannot display GEOGRAPHY data that crosses that date line, without a hack such as making a table of split geographies.

Does anyone disagree? (please disagree...!)

Thanks, James

On 12 October 2012 17:47, Paul Ramsey-4 [via PostGIS] <[hidden email]> wrote:

Even if you split the shapes, GEarth renders polygons in a non-normal
kind of way which you might find unacceptable

http://blog.opengeo.org/2010/08/10/shape-of-a-polygon/

The quick fix is to render them as lines, not polygons. there's no fix
to get them to fill using great circle edges, GEarth just doesn't work
that way.

P.

On Fri, Oct 12, 2012 at 4:03 AM, iam_gilbey <[hidden email]> wrote:

> I have many polygons, including several that cross the date line. They are
> stored as GEOGRAPHY and work perfectly with PostGIS v2.0.1, PostgreSQL 9.1.3
> on windows XP. I can serve this data using Geoserver (v2.1), and view it
> using open layers, where the polygons crossing the date line render
> correctly.
>
> I cannot however convert the data into KML (viewed in Google Earth 5.1), or
> view it in Quantum GIS (v1.7), without the date line polygons being wrapped
> around the earth.
>
> I appreciate that this isn't strictly a postGIS problem, however being faced
> with the stark choice between splitting my data about the date line
> (inelegant) or not using Google Earth (unacceptable to users), I don't know
> where else to turn!
>
> Do you know of:
> a) a way to get the data to render correctly in Google Earth; or
> b) where else I should ask?
>
> Thanks!
>
>
>
> --
> View this message in context: http://postgis.17.n6.nabble.com/Display-GEOGRAPHY-polygons-crossing-date-line-tp5000443.html

> Sent from the PostGIS - User mailing list archive at Nabble.com.
> _______________________________________________
> postgis-users mailing list

> [hidden email]
> http://postgis.refractions.net/mailman/listinfo/postgis-users

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View this message in context: Re: Display GEOGRAPHY polygons crossing date line

[Paul Ramsey]

GEarth cannot display geography *POLYGONS* that cross the dateline. It
can display linestrings just fine.

P.

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