[postgis-users] ST_Intersects

[Paul Ramsey]

It seems to me that the only way out of this conundrum (people with
"boxes" they drew on projected maps) is to provide some densification
functions so they can force their geometries to be closer to what they
want by filling in points.  Both geometry and geography could use some
densification routines.

P.

On Tue, Jun 14, 2011 at 2:11 AM, Mahesh Ghule <mahesh.ghule at gmail.com> wrote:
> Thanks a bunch Paul.
> I did arrive those findings after I posted the query.
> Now I am thinking how to do what I want to do if I want the polygon to be
> with the great circles in postgis.
> Any pointers.
> Regards,
> Mahesh
> On 13 June 2011 17:49, Paul Ramsey <pramsey at opengeo.org> wrote:
>>
>> 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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