Thank you Paul for the precision. Did you think I can find a way (finding the nearest neighboor in 3d) with some of the st_ function ? Or should I wait as you talk about in http://www.mail-archive.com/[email protected]/msg08026.html
Or should I go and use other tools like grass/R ? Thanks. Paul Ramsey wrote: > PostGIS is "2.5D", not 3D, which means that, while Z and M coordinates > are available to store data, they are not used in calculations (with a > few exceptions, for things like linear referencing), they are just > carried along for the ride. Hence what you are observing. > > The "box3d" name is confusing and dates back to the 0.X series of > PostGIS, which stored 3 dimensions at all times, even when only two > dimensions existed in the data (in which case the 3rd dimension was > zeroed and hidden in output). The bounding box for such a 3-d > structure would naturally be named, "box3d". But it was never used for > 3d calculation, despite the name. > > P. > > On Sat, Sep 12, 2009 at 9:39 AM, Bruno Friedmann <[email protected]> wrote: >> Hi All >> >> I'm facing strange results which I can't explain. >> So any help or idea are welcome. >> >> Here the context >> Table of point in 3d have been setup. >> >> >> SELECT >> st_asewkt(the_geom), >> GeometryType(the_geom), >> NDims(the_geom), >> ZMFlag(the_geom) >> from dom limit 2; >> >> which seems to return correct 3d point >> >> "SRID=21781;POINT(602499.98 233307.35 1026.73)";"POINT";3;2 >> "SRID=21781;POINT(602499.98 233326.89 1046.81)";"POINT";3;2 >> >> >> The full extend of data is >> "BOX3D(598125 233000 631.03,602499.98 235999.98 1316.91)" >> >> Now I try to select rows inside a predefined box >> >> select id,est,nord,alti_u from dom_1106_42_03 >> WHERE st_within( >> the_geom, >> st_setsrid( >> st_makebox3d ( >> GeomFromEWKT('SRID=21781;POINT( 598995 233995 500)'), >> GeomFromEWKT('SRID=21781;POINT( 599005 234005 1000)') >> ) >> ,21781) >> ) >> >> In this part alti Z is not above 1200 meters so I should not find anything >> but I've got results like this : >> >> id est nord alti >> 2774523;598995.1600;234002.1500;1209.8700 >> 2775215;598995.3800;234001.0900;1210.2600 >> 2775297;598995.4000;233999.6300;1207.7600 >> >> It's ok for x,y but not Z >> I don't understand where my problem reside. >> >> Thanks a lot in advance. >> >> _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
