[postgis-users] NAD conversion problem

[Peter N. Schweitzer]

Richard Greenwood wrote:
> On Thu, Dec 4, 2008 at 1:19 PM, Peter N. Schweitzer
> <pschweitzer at usgs.gov> wrote:
>> Hello,
>>
>> I have two PostgreSQL installations.  One uses 8.3.3 with PostGIS 1.3.3,
>> GEOS 3.0.1, and PROJ 4.6.1 (with proj-datumgrid-1.4).  With it I am able to
>> run a command like
>>
>> update county set nad27_geom=ST_Transform(the_geom,4267);
>>
>> My newer installation uses 8.3.5 with PostGIS 1.3.4, GEOS 3.0.3, and
>> PROJ 4.6.1.  With this system I get the error message
>>
>> WARNING:  transform: -38 (failed to load NAD27-83 correction file)
>> ERROR:  transform: couldn't project point: -38 (failed to load NAD27-83
>> correction file)
>>
>> I know that proj-datumgrid-1.4.zip must be unzipped in the nad/
>> directory of proj-4.6.1 PRIOR to running configure.  I have done this.
>> I have also recompiled and reinstalled proj, GEOS, and PostGIS in that
>> order, running ldconfig at the end of each step.  The directory
>> /usr/local/share/proj on each of these systems is identical.
>>
>> I've tried recreating the database cluster, starting and stopping
>> the database instance, rebooting the machine, dropping and rebuilding
>> the spatial database, all to no avail.
>>
>> So I'm looking for some setting that I may have missed, some environment
>> variable, or some trick to tell libproj.so.0.5.5 where its transform
>> files should go.
>>
>> Both systems run Slackware 12.1.
>>
>> I'm at wit's end.  Any clues?
>>
>> Pete
> 
> PROJ_LIB is an environment variable that points to the directory
> containing grid shift files and EPSG parameter files.
> 
> The grid shift files are binary and platform specific. Is it possible
> that you are using Windows grid shift files on a Linux system?
> 
> You could also rule out issues related to the different versions of
> Postgres and PostGIS on you two systems by testing at the command line
> with the cs2cs utility which is a part of Proj.

Rich,

Thanks for your counsel.  The example using cs2cs from its documentation
worked the same on both systems, executed from the command line.

I believe the grid shift files are slightly different, even though I
thought I had installed the same versions.  As a test, I copied the
/usr/local/share/proj directory from the older system (the one that
does the datum shift without complaint) to the newer one, and the
ST_Transform completes without error.  So I believe that is the source
of the problem.

But there is only one link on http://trac.osgeo.org/proj/ for the 
datum shift file package.  If the package is OS-specific I would
expect to see more than one.  So I am puzzled and worried that next
time I may face the same problem again.

Peter
-- 
Peter N. Schweitzer (MS 954, U.S. Geological Survey, Reston, VA 20192)
(703) 648-6533  FAX: (703) 648-6252  email: pschweitzer at usgs.gov
<http://geology.usgs.gov/peter/>