[postgis-users] Display GEOGRAPHY polygons crossing date line

Paul Ramsey pramsey at opengeo.org
Tue Oct 16 07:17:24 PDT 2012


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

P.

On Tue, Oct 16, 2012 at 2:54 AM, iam_gilbey <simonbolivar.uk at gmail.com> wrote:
> 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!
>> >
>> >
>> >
>> > --
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