On Tue, May 11, 2010 at 4:30 PM, Nicholas Bower <n...@petangent.net> wrote: > > On 12 May 2010 08:14, Paul Ramsey <pram...@opengeo.org> wrote: >> >> The doc example appears to not mention the limitation in the geography >> implementation, which can be fixed. The example is correct, insofar >> as it is against geometries, but again, doesn't illustrate the >> limitation in the geography implementation. > > I see that would explain it. So how do I actually determine if 1 geography > polygon is wholly inside another (on the WGS spheroid)?
Right now you don't. You've got intersects on all types, but that's it. I can provide a quote if you want to fund the work. Workarounds would including testing for index interaction in geography land, then flipping both candidates out to a "suitable" projection for a test in geometry land. See the ST_Buffer(geography) implementation for an example of that approach. This would avoid the singularity issues around the poles/dateline, but would fail for very large (geographic size-wise) objects. P. >> >> You can cast geography to geometry and use the function that way but >> be forewarned about any shape that crosses the datesline/poles or has >> very long edges. > > Not an option - this warning is precisely why I spent substantial effort > migrating our DB out of 1.3 geometries into 1.5 geographies. We have global > satellite views that cross the IDL, and intersections of spatial regions > nowhere near these shapes were previously returning true using geometries > (wrapping the wrong way around the Earth). > Am very grateful for geographies - just need a way to do the query with 2 > polygons... > > >> >> On Tue, May 11, 2010 at 3:06 PM, Nick Bower <n...@petangent.net> wrote: >> > Thanks but not according to the doc I think? >> > 1) Abstract superclass is mentioned in API, not point, >> > 2) the SQL example uses circles >> > 3) the blog link specifically uses polygons in it's discussion of OGC >> > coverage behaviour. >> > >> > >> > http://postgis.refractions.net/documentation/manual-1.5/ST_CoveredBy.html >> > >> > I'm not disputing your explanation given the evidence, but suggest the >> > docs >> > are entirely misleading for me figuring out if one polygon geography is >> > wholey inside another. >> > >> > >> > On 11/05/2010, at 11:48 PM, Paul Ramsey <pram...@opengeo.org> wrote: >> > >> >> Bad sentence construction in the error, perhaps? The restriction "only >> >> polygon and point" means that one argument must be a polygon and one >> >> must be a point. Both your arguments are polygons. >> >> >> >> P. >> >> >> >> On Tue, May 11, 2010 at 4:51 AM, Nicholas Bower <n...@petangent.net> >> >> wrote: >> >>> >> >>> I've read the 1.5 reference docs but can't figure out what is wrong >> >>> with >> >>> below. ST_CoveredBy(geography, geography) should work right? >> >>> select count(*) from t_swath_metadata where ST_CoveredBy( >> >>> ST_GeogFromText('SRID=4326;POLYGON((123.1773295292851 >> >>> -16.07501950971949, >> >>> 122.745660066063 -16.83965661151543, >> >>> 124.1310486688905 -16.44978157737539, >> >>> 123.1773295292851 -16.07501950971949))'), >> >>> swath_bounding); >> >>> ERROR: geography_covers: only POLYGON and POINT types are currently >> >>> supported >> >>> CONTEXT: SQL function "st_covers" statement 1 >> >>> ********** Error ********** >> >>> ERROR: geography_covers: only POLYGON and POINT types are currently >> >>> supported >> >>> SQL state: XX000 >> >>> Context: SQL function "st_covers" statement 1 >> >>> >> >>> db=> \d t_swath_metadata; >> >>> ... >> >>> swath_bounding | geography(Polygon,4326) | >> >>> Indexes: >> >>> ... >> >>> "t_swath_metadata_swath_bounding_key" gist (swath_bounding) >> >>> >> >>> Thanks, Nick >> >>> >> >>> _______________________________________________ >> >>> postgis-users mailing list >> >>> postgis-users@postgis.refractions.net >> >>> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >>> >> >>> >> >> _______________________________________________ >> >> postgis-users mailing list >> >> postgis-users@postgis.refractions.net >> >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> > >> > _______________________________________________ >> > postgis-users mailing list >> > postgis-users@postgis.refractions.net >> > http://postgis.refractions.net/mailman/listinfo/postgis-users >> > >> _______________________________________________ >> postgis-users mailing list >> postgis-users@postgis.refractions.net >> http://postgis.refractions.net/mailman/listinfo/postgis-users > > > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users > > _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users