Disregard this last question if its not a trivial one. We just decided not to use this projection for this project since it renders differently under proj 4.5 than 4.6 and found one that seems to work for us that will render the same under both.
Our main concern was not so much that we keep data in 2163 projection, but that a lot of the tools we use are compiled with the older proj library and we didn't want to change that at this moment. So this little difference in behavior would cause potential problems when reprojecting non-postgis data. Thanks, Regina -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Paragon Corporation Sent: Tuesday, January 29, 2008 9:12 AM To: 'PostGIS Users Discussion' Subject: RE: [postgis-users] Weird behavior transforming from srid 4269 to 2163 Anyway to make the new bahave like the old? -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Frank Warmerdam Sent: Tuesday, January 29, 2008 8:40 AM To: PostGIS Users Discussion Subject: Re: [postgis-users] Weird behavior transforming from srid 4269 to 2163 Paragon Corporation wrote: > I'm having some strange discrepancies between two postgis servers in > how they are transforming the same data from 4269 to 2163. I'm hoping > someone could shade some light on what could be the problem. > > The problematic server is running Red Hat 4.1.2-14 and postgis version > "POSTGIS="1.3.2" GEOS="2.2.3-CAPI-1.1.1" PROJ="Rel. 4.6.0, 21 Dec 2007" > USE_STATS" > > The one that I think is right is running Windows 2003 server > "POSTGIS="1.3.1" GEOS="3.0.0rc4-CAPI-1.3.3" PROJ="Rel. 4.5.0, 22 Oct 2006" > USE_STATS" > > So the bad one is running a newer version of the PROJ library, but I > wasn't the one who compiled and installed, so not sure if there was a > step missing. Regina, I suspect your EPSG:2163 is evaluating to: +proj=laea +lat_0=45 +lon_0=-100 +x_0=0 +y_0=0 +a=6370997 +b=6370997 +units=m +no_defs In PROJ 4.5 the transformation from EPSG:4269 (NAD83) to EPSG:2163 would be accomplished by transforming NAD83 coordinates into geocentric coordinates and then back into lat/long on the EPSG:2163 ellipsoid resulting in a substantial shift in latitude. However, after a half a decade of complaints about this "default ellipsoid conversion" which is usually the wrong thing to do, PROJ 4.6 finally changed the behavior to doing no datum shift if either the source or the destination lacks apparent datum shift information. That means, in this case, that the input coordinates are being used as if they were already on the spherical ellipsoid and no datum/spheroid shift operation is done. I really think this is the appropriate change in your case, but it is certainly a change in behavior. It may also not agree with data previously converted to EPSG:2163. Best regards, -- ---------------------------------------+-------------------------------- ---------------------------------------+------ I set the clouds in motion - turn up | Frank Warmerdam, [EMAIL PROTECTED] light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | President OSGeo, http://osgeo.org _______________________________________________ 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
