[postgis-users] Problem with ST_WITHIN
Luigi Castro Cardeles
luigi.cardeles at gmail.com
Mon Sep 21 10:47:23 PDT 2009
Hi list and Martin,
many thanks :D
[]'s
Luigi Castro Cardeles
2009/9/21 Martin Davis <mbdavis at refractions.net>
> Switch the arguments around.
> ST_covers(A, B) = true iff A covers B
> In other words, ST_covers(LINE, POLYGON) = false, but ST_covers(POLYGON,
> LINE) = true.
>
> In other other words, the order of the arguments for ST_covers should be
> the same as for ST_within, and opposite to ST_contains
>
> Luigi Castro Cardeles wrote:
>
>> Hi list and Martin,
>>
>> If i use st_covers, the query 1 and 2 return's false.
>> After read the blog, i am thinking that covers should return true at that
>> cases.
>> query 1:
>> select ST_covers
>> (
>> geomfromtext('LINESTRING(10 18, 30 18)',4326),
>> geomfromtext('MULTIPOLYGON (((10 18,30 18,30 12,10 12,10
>> 18)))',4326)
>> )
>>
>> and
>>
>> query 2:
>> select ST_covers
>> (
>> geomfromtext('POINT(10 18)',4326),
>> geomfromtext('MULTIPOLYGON (((10 18,30 18,30 12,10 12,10
>> 18)))',4326)
>> )
>>
>>
>> select postgis_full_version();
>> "POSTGIS="1.3.6" GEOS="3.1.0-CAPI-1.5.0" PROJ="Rel. 4.6.1, 21 August 2008"
>> USE_STATS"
>> I am using postgres 8.3.7 version and windows vista os.
>>
>> I read the release notes and the bug tracker and don't find any bug that
>> fit the problem.
>>
>> In the meanwhile, i will download the postgres 8.3.8, 8.4.1 and try with
>> newer versions of postgis 1.4.0 etc.
>>
>> Anyone has any clues?
>>
>> very thanks for yout help,
>> Luigi Castro Cardeles
>>
>>
>> 2009/9/21 Martin Davis <mbdavis at refractions.net <mailto:
>> mbdavis at refractions.net>>
>>
>>
>> The OGC definition for Contains and Within have always seemed a
>> bit non-intuitive to me. They may be theoretically elegant. but
>> they don't really address the most common use case. (See a blog
>> post on this as:
>>
>> http://lin-ear-th-inking.blogspot.com/2007/06/subtleties-of-ogc-covers-spatial.html
>> ).
>>
>> That's why JTS, GEOS and PostGIS define the covers() predicate,
>> which has simpler, more intuitive and more practical semantics.
>>
>> http://postgis.refractions.net/documentation/manual-1.4/ST_Covers.html
>>
>>
>> Luigi Castro Cardeles wrote:
>>
>> Hi list and Chris,
>>
>> this is what i was asking :D
>>
>> i was thinking that boundary is part of the geometry, so if
>> there is some geometry on the boundary (in this case, a point
>> on the polygon boundary) then the point is within the polygon.
>> But after your message i read the specs
>> (http://portal.opengeospatial.org/files/?artifact_id=18241)
>> about within, i see the relate and now i understand. Thanks
>> for the hint Chris.
>>
>> []'s
>> Luigi Castro Cardeles
>>
>>
>> 2009/9/18 Chris Hermansen <chris.hermansen at timberline.ca
>> <mailto:chris.hermansen at timberline.ca>
>> <mailto:chris.hermansen at timberline.ca
>> <mailto:chris.hermansen at timberline.ca>>>
>>
>>
>> If it's on the boundary, is it within?
>> Chris Hermansen chris.hermansen at timberline.ca
>> <mailto:chris.hermansen at timberline.ca>
>> <mailto:chris.hermansen at timberline.ca
>> <mailto:chris.hermansen at timberline.ca>>
>>
>> tel+1.604.714.2878 · fax+1.604.733.0631 · mob+1.778.840.4625
>> Timberline Natural Resource Group · www.timberline.ca
>> <http://www.timberline.ca>
>> <http://www.timberline.ca>
>>
>> 401 · 958 West 8th Avenue · Vancouver BC · Canada · V5Z 1E5
>>
>>
>> -----Original Message-----
>> From: Luigi Castro Cardeles <luigi.cardeles at gmail.com
>> <mailto:luigi.cardeles at gmail.com>
>> <mailto:luigi.cardeles at gmail.com
>> <mailto:luigi.cardeles at gmail.com>>>
>>
>> Date: Fri, 18 Sep 2009 10:01:32
>> To: PostGIS Users
>> Discussion<postgis-users at postgis.refractions.net
>> <mailto:postgis-users at postgis.refractions.net>
>> <mailto:postgis-users at postgis.refractions.net
>> <mailto:postgis-users at postgis.refractions.net>>>
>> Subject: Re: [postgis-users] Problem with ST_WITHIN
>>
>>
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>> -- Martin Davis
>> Senior Technical Architect
>> Refractions Research, Inc.
>> (250) 383-3022
>>
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>
> --
> Martin Davis
> Senior Technical Architect
> Refractions Research, Inc.
> (250) 383-3022
>
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