[postgis-users] ST_Intersects

[Paul Ramsey]

And relatedly, here's why Google Earth gives the wrong visual answer.

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

P.

On Mon, Jun 13, 2011 at 9:47 AM, Paul Ramsey <pramsey at opengeo.org> wrote:
> You're thinking in straight lines, not great circles. Here's what your
> "box" actually looks like
>
> http://www.gcmap.com/mapui?P=10N+170E-10N+0E%2C%0D%0A10N+170E-5N+170E%2C%0D%0A5N+170E-5N+0E%2C%0D%0A5N+0E-10N+0E&MS=wls&DU=mi
>
> I can see how that could hit your Russian foot print.
>
> P.
>
> On Mon, Jun 13, 2011 at 6:54 AM, Mahesh Ghule <mahesh.ghule at gmail.com> wrote:
>> Hello Guys,
>> After lot of head scratching I have decided to post this email.
>> We have a PostGIS 1.5.1 on PostgreSQL 8.4
>> select
>> ST_AsText('0105000020E6100000010000000102000000020000009FAEEE586C8C5240029CDEC5FBF94D406B44300E2EDB5140D591239D81D14C40'::geography)
>> as TextFootPrint,
>>
>>  ST_Intersects('0105000020E6100000010000000102000000020000009FAEEE586C8C5240029CDEC5FBF94D406B44300E2EDB5140D591239D81D14C40'::geography,
>> ST_GeographyFromText('POLYGON((0 10,170 10,170 5,0 5,0 10))')) as
>> Intersects;
>> yields following result
>> TextFootPrint
>>                   |          Intersects
>> -------------------------------------------------------------------------------------------------------------------
>> MULTILINESTRING((74.194113 59.952996,71.424686 57.636768))      |          t
>>
>> Which as I understand is not correct. The footprint is a line string
>> somewhere over Russia and the Polygon is a band in north hemisphere just
>> above equator.
>> Also when I visualise the both geographies as KML in google earth I can see
>> them thousands of miles apart.
>> This is just one example footprint where I have tens of thousand more in my
>> DB like this.
>> Please help me understand what is going on?
>>
>> Regards,
>> Mahesh
>>
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>>
>