On Thursday 11 December 2008, Peter N. Schweitzer wrote: > Dylan Beaudette wrote: > > Strange. I have never modified that code before, and regularly get the > > correct output... I will post back with a similar example that causes > > PostGIS to throw the '-38' error. > > Dylan, > > Another correspondent indicated to me that when he applied this change, > he got different, better results even though he wasn't seeing this > specific error message (perhaps because he wasn't at the psql prompt > when the transform operation occurred). We're both running Linux. > > How do you know what the correct output is? > > Peter
Hi Peter, It is always good to check on what you think software is doing. Checking with proj4 (Rel. 4.6.0, 21 Dec 2007) -- linux / compiled from source # compute shift from NAD27 -> NAD83 echo '-121.000000 37.000000' | cs2cs +proj=latlong +datum=NAD27 \ +to +proj=latlong +datum=NAD83 # result: first in DD, then DMS -121.001029 36.999945 121d0'3.704"W 36d59'59.804"N # result from NADCON # http://www.ngs.noaa.gov/cgi-bin/nadcon.prl NAD 27 datum values: 37 00 0.00000 121 00 0.00000 NAD 83 datum values: 36 59 59.80376 121 00 3.70364 Looks pretty close to me. Lets check PostGIS, compiled with Proj4 support: -- convert NAD27 -> NAD83 SELECT AsText( ST_Transform(SetSRID(ST_MakePoint(-121.000000,37.000000), 4267), 4269) ) ; astext ------------------------------------------- POINT(-121.001028788906 36.9999454900731) Looks close to the output from proj4 above. Thoughts? Dylan -- Dylan Beaudette Soil Resource Laboratory http://casoilresource.lawr.ucdavis.edu/ University of California at Davis 530.754.7341 _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
