Hi Nicklas Actually the points can be outside the polygon and returning true but it can be tolerance about 1 meters outside. I'm using SRID: 4326. I would like to know 0.00001 with the projection 4326 is equal 1 meter or not ?
I used ST_Intersects (geom, geometry); but it's really slow, I don't know why. I also used ST_Dwithin (geom, geometry, 0) and the result is empty, i couldn't found any neighbour. Cheers On Tue, May 25, 2010 at 3:22 PM, Nicklas Avén <[email protected]>wrote: > Hallo > > What you are doing with ST_Dwithin is to check if your geom and geometry > have parts closer to (or exactly) 0.00001 mapunits from eachother. If you > are using a meter based SRID then you are checking if they are within > 0.00001 meters from eachother. So actually in this case your points can be > just outside the polygon and returning true. If you want to use st_dwithin > you should use 0 instead of 0.00001 . But I don't think that is any faster > than ST_Intersects. The important thing in both cases is to have working > spatial indexes. > > put an index on geom column in my_neighbour table and analyze the table. > > Create index idx_mn_geom > on my_neighbour > using gist(geom); > analyse my_neighbour; > > Then try: > > SELECT id, geom > FROM my_neighbour > WHERE ST_Intersects (geom, geometry); > > I guess that is the best solution. > > Hope that helps > > Nicklas > > > 2010-05-25 nguyen liem wrote: > > Hi all > > > >At the first time i used ST_Contains but it take a long time, so I used > ST_Dwithin to improve the performance for the query statement but i don't > know it is correct or not. > >I would like to know my points are within in polygon or not: > > > >SELECT id, geom > >FROM my_neighbour > >WHERE ST_Dwithin (geom, geometry, 0.00001) > > > >geometry: is a polygon(input parameter). > >0.00001: I means the radius of geometry is 1 meters, is it right? > > > > > >Cheers. > > > >-- > >Liem Nguyen > >Developer > >Axon Active Corp. > > >---------------------------------------------------------------------------- > >Direct Line : +84 38 948 4645 > >Fax : +84 38 811 3489 > > Mobile Phone : +84 168 994 8897 > >Skype ID : liemnguyendl2204 > >Email : [email protected] / [email protected] > > Web Site : axonactive.vn > > >Address : 87 Thang Long Street,Gate 2 Ward 4, > > Tan Binh District, HCM city, Vietnam. > > > > > > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > > -- Liem Nguyen Developer Axon Active Corp. ---------------------------------------------------------------------------- Direct Line : +84 38 948 4645 Fax : +84 38 811 3489 Mobile Phone : +84 168 994 8897 Skype ID : liemnguyendl2204 Email : [email protected] / [email protected] Web Site : http://axonactive.vn Address : 87 Thang Long Street,Gate 2 Ward 4, Tan Binh District, HCM city, Vietnam.
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