Thanks for your reply Paul. Yes, that's what I thought. That would explain why (0,-82) is inside the polygon. Nevertheless, if my first segment runs through the south pole, then I would expect both of the queries mentioned in my initial post to return 0 which is not the case.
Sebastien On Mon, Feb 20, 2017 at 4:56 PM, Paul Ramsey <[email protected]> wrote: > I don't the polygon you've draw means what you think it does. > > POLYGON((-90 -80, 90 -80, 90 10, -90 10, -90 -80)) > > For example, you probably figure the first segment, -90 -80, 90 -80 runs > east-west between two points close to the south pole. In fact, it runs > directly over the south pole, so actually to the south of your point of > interest. > > P > > > On Sun, Feb 19, 2017 at 7:36 PM, Sebastien Delaux <[email protected] > > wrote: > >> Hi all, >> >> I am new to postgis and I am interested in finding all the points that >> are located at x metres or less of a polygon that are stored in my postgres >> database. >> As I am working with data located all over the world and want to work >> with distances in metres I decided to use the geography type. >> >> I am trying to understand why the following query returns 0 when the >> point is clearly not included in the polygon: >> SELECT ST_Distance(ST_GeographyFromText('SRID=4326;POINT(0. >> -82.)'),ST_GeographyFromText('SRID=4326;POLYGON((-90 -80, 90 -80, 90 10, >> -90 10, -90 -80))')); >> >> I suspect this has something to do with the polygon crossing the equator >> as >> SELECT ST_Distance(ST_GeographyFromText('SRID=4326;POINT(0. >> -82.)'),ST_GeographyFromText('SRID=4326;POLYGON((-90 -80, 90 -80, 90 >> -10, -90 -10, -90 -80))')); >> returns a plausible distance. >> >> Would anybody know whether my polygon is violating some assumption or >> whether there is any other reason that I am getting those results? >> >> Thanks >> >> Sebastien >> >> >> >> >> >> >> >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> https://lists.osgeo.org/mailman/listinfo/postgis-users >> > > > _______________________________________________ > postgis-users mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/postgis-users >
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