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 <[email protected]
<mailto:[email protected]>>
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 <[email protected]
<mailto:[email protected]>
<mailto:[email protected]
<mailto:[email protected]>>>
If it's on the boundary, is it within?
Chris Hermansen [email protected]
<mailto:[email protected]>
<mailto:[email protected]
<mailto:[email protected]>>
tel+1.604.714.2878 · fax+1.604.733.0631 · mob+1.778.840.4625
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-----Original Message-----
From: Luigi Castro Cardeles <[email protected]
<mailto:[email protected]>
<mailto:[email protected]
<mailto:[email protected]>>>
Date: Fri, 18 Sep 2009 10:01:32
To: PostGIS Users
Discussion<[email protected]
<mailto:[email protected]>
<mailto:[email protected]
<mailto:[email protected]>>>
Subject: Re: [postgis-users] Problem with ST_WITHIN
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