[postgis-users] Question on datum names

[Peter N. Schweitzer]

Thanks, Frank!

I conclude there is little to lose in using ESRI's names for projection,
datum, and spheroid, so that my .prj files will work without modification
in ArcGIS.  I'm puzzled that these texts, evidently a controlled vocabulary
lacking formal standardization, play such a strong role, but if it makes
things work and doesn't break much, it's clearly a better approach.

Peter

On 05/29/2012 05:56 PM, Frank Warmerdam wrote:
> Peter,
> 
> I agree that it is somewhat perverse to use the .prj extension if you
> aren't going to match ArcGIS PE strings.  Either call it something
> else (like .pgwkt for instance) or transform it.  The GDAL/OGR
> packages' OGRSpatialReference class includes a morphToESRI() method
> that will convert OGC/PostGIS/OGR Well Known Text to ESRI PE String
> format reasonably well.
> 
> On Tue, May 29, 2012 at 2:45 PM, Peter N. Schweitzer
> <pschweitzer at usgs.gov> wrote:
>> On the web site from which I distribute spatial data, I provide shapefiles
>> with projection information as a .prj file.  I've drawn the contents of
>> these prj files from the srtext field of the spatial_ref_sys table.
>>
>> A user has pointed out to me that this is inconvenient for people running
>> ArcGIS because ArcGIS expects to see different values as the name of the
>> coordinate system and the datum.  I have not seen a standard that specifies
>> these names.  Is there one?
> 
> Well, the defacto standard is whatever ArcGIS does.  They do publish
> various information on this but it isn't a "standard" in the normal sense of
> that world.  Note that OGC's Well Known Text format was an adaption of
> ESRI PE Strings - hence the similar but not the same nature.
> 
> Best regards,
> Frank
> 
>> It looks like I could change my .prj files to fit ArcGIS without much trouble.
>> But would this change break other applications?  Are there GIS applications
>> other than ArcGIS that rely strongly on these names?  How do others support
>> portability of projection information in downloadable data using the shapefile
>> format?
>>
>> 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/>