[postgis-users] Problems with PostGIS and Proj4 on Cygwin

Dave Blasby dblasby at refractions.net
Tue Jun 4 16:34:14 PDT 2002


> Any ideas what could cause the problems on Cygwin? Problems with the Proj 4
> installation?

I just recently added some code to PostGIS that covers up a 'feature' of
proj4.  
If you attempt to do a NAD conversion for a point were there is no 'grid
nad converting data', PROJ4 will fail.  I recently patched PostGIS so
that it will re-try the projection w/o the NAD conversion. 
Unfortunately there is no way to get it to do a ellipsoid conversion w/o
doing a NAD conversion.  Perhaps your 2 version of postgis are
different?

Also, make sure you're using PROJ4.4.5 (not 4.4.4) because its NAD
conversion is incorrect.

PROJ4, by default, only actually uses the conus (the lower 48 states)
and basic canadian 'grid nad converting data' - you have to modify one
of PROJ4's .c files (pj_datums.c) to get it to use other ones.

I dont know of any differences between the linux and windows versions of
PROJ4.  What is the version number used by windows?  Which version of
PostGIS are you using?

dave




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