Can you show us your queries? Some of these examples look a little funny -- i.e. did you query contain the ST_xxx() function in the JOIN condition and the gometry construction?
-- like this: select st_intersection(a,b) from t1 join t2 on st_intersects(a,b) ; Dylan On Thursday 04 December 2008, William Kyngesburye wrote: > When I was debugging my invalid geometry problem, I needed to select a > small area to view. The data is divided up into 1 degree tiles (it's > the SRTM SWBD shapefiles imported). I figured selecting by whole > integer degrees would be simple to deal with. > > I started with st_overlaps(), as it was mentioned in the wiki I think, > or somewhere online (this was a few weeks ago, and don't remember the > details). But it was not selecting very much at all in a large area. > I looked at the PostGIS documentation to see what other functions > would work, but their descriptions are not plain english and and tried > them all. And there was a pointer to: > > http://lin-ear-th-inking.blogspot.com/2007/06/subtleties-of-ogc-covers-spat >ial.html > > that helped a little. But none of the ones I tried gave me what I > want - polygon areas completely inside the box boundary and area, and > not polygons where only the boundary touches the box boundary. > > Snapshots: > > http://www.kyngchaos.com/wiki/gallery:gis:temp:index > > ST_Overlaps() -- only polygons selected where their boundaries touch > the box boundary and any part of the polygon area is inside the box. > I get none that are completely within but not touching are selected. > > ST_Intersects() -- all polygons selected where //any// part of the > polygon (boundary and inside) are in or touch //any// part of the box, > though it seems to have missed some from the upper-right neighboring > cells. A lot more than I want. > > ST_CoveredBy() -- only polygons where the boundary //and// area are > completely inside only the area of the box and not touching the box > boundary. I don't get the polys touching the box edge. > > ST_Within() -- similar to st_coveredby, except that it only seems to > look at the outer boundary of the polygons, and that upper-right > corner polygon is actually an invalid polygon where the "outer" > polygon is a "hole" polygon (not visible here), thus inside and not > touching the box boundary. > > > Did I miss an obvious function, or is there something that will get > what I want? hmmm, maybe a combination (but would that slow it down a > lot)? > > ----- > William Kyngesburye <kyngchaos*at*kyngchaos*dot*com> > http://www.kyngchaos.com/ > > [Trillian] What are you supposed to do WITH a maniacally depressed > robot? > > [Marvin] You think you have problems? What are you supposed to do if > you ARE a maniacally depressed robot? No, don't try and answer, I'm > 50,000 times more intelligent than you and even I don't know the > answer... > > - HitchHiker's Guide to the Galaxy > > > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users -- Dylan Beaudette Soil Resource Laboratory http://casoilresource.lawr.ucdavis.edu/ University of California at Davis 530.754.7341 _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
