Hmm. The earth is 40000km in circumference, / 360 degrees is about 110 km per degree.
These two points are 1E-11 degrees apart, times 1E5 meters/degree, or about 1E-6 meters. Seems pretty close to me. Over and above that, I would guess that PostGIS uses some kind of tolerance to compare for equality, and your coordinates are equal to 12+ decimal places. Or am I missing something? Chris Hermansen [email protected] tel+1.604.714.2878 · fax+1.604.733.0631 · mob+1.778.840.4625 Timberline Natural Resource Group · www.timberline.ca 401 · 958 West 8th Avenue · Vancouver BC · Canada · V5Z 1E5 -----Original Message----- From: Blake Crosby <[email protected]> Date: Sat, 12 Sep 2009 09:39:46 To: PostGIS Users Discussion<[email protected]> Subject: Re: [postgis-users] st_isvalid() does not return warning message Chris, I hope this isn't the problem. Cause really: (-108.616666666667 54.2) != (-108.616666666664 54.1999999999825) Here is what the shape looks like: http://www.blakecrosby.com/shape.jpg Blake Chris Hermansen wrote: > Blake, I haven't sketched it out but it looks like two points are nearly on > top of one another - at -108.616666666667 54.2,-108.616666666664 > 54.1999999999825 > > And later at > -108.683333333331 > 54.766666666652,-108.683333333333 54.7666666666667 > > Could this be your problem? > ------Original Message------ > From: Blake Crosby > Sender: [email protected] > To: PostGIS Users Discussion > ReplyTo: PostGIS Users Discussion > Subject: [postgis-users] st_isvalid() does not return warning message > Sent: Sep 11, 2009 22:02 > > Hello, > > I'm trying to figure out why some of my geometries are not valid. > > Take the following geo: > > POLYGON((-111.066666666667 56.0666666666667,-110.3 > 56.5,-107.916666666667 56.5,-106.833333333333 > 56.1166666666667,-106.833333333333 54.2833333333333,-107 > 54.2,-108.616666666667 54.2,-108.616666666664 > 54.1999999999825,-108.600299787004 54.2475512622716,-108.58790183346 > 54.29551368139,-108.579516153242 54.3437730783836,-108.575176879509 > 54.392214173427,-108.574908719816 54.4407208506564,-108.578726762226 > 54.4891764287016,-108.586636300775 54.5374639364321,-108.598632681986 > 54.5854663933806,-108.614701174154 54.6330670942644,-108.634816861126 > 54.6801498969695,-108.658944562284 54.7265995133165,-108.683333333331 > 54.766666666652,-108.683333333333 54.7666666666667,-108.433333333333 > 54.9333333333333,-108.433333333333 55.3333333333333,-108.433333333333 > 56.0666666666667,-111.066666666667 56.0666666666667)) > > st_issimple() returns true, while st_isvalid() returns false. The > st_isvalid() documentation states that the PGSQL Warning message will > let me know why its invalid, but it does not: > > flightplan=> select st_isvalid(geometry) from airspace where id='238'; > st_isvalid > ------------ > f > > Any way I can figure out why this geometry isn't valid? Postgis version 1.3: > > flightplan=> select postgis_version(); > postgis_version > --------------------------------------- > 1.3 USE_GEOS=1 USE_PROJ=1 USE_STATS=1 >_______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > > > Chris Hermansen [email protected] > tel+1.604.714.2878 · fax+1.604.733.0631 · mob+1.778.840.4625 > Timberline Natural Resource Group · www.timberline.ca > 401 · 958 West 8th Avenue · Vancouver BC · Canada · V5Z 1E5 >_______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
