[postgis-users] prj and SRID relation

[Frank Warmerdam]

Paul Ramsey wrote:
> Frank Warmerdam wrote:
> 
>> I would add that implementing WKT to PROJ.4 translation isn't
>> terribly hard, but it is significantly harder to keep up with
>> variations in WKT input from different sources, especially ESRI.
>> Have to maintain multiple copies of this sort of stuff would be quite
>> a hassle for all involved.  My maintaining one copy of it is already
>> quite a hassle!
> 
> 
> Just by way of an aside, does OGR ever use the WKT in the absence of 
> proj4? I just find it odd that the library that needs the ability to 
> parse the serialized form (proj4) is not the library that actually has 
> the ability. Could you be persuaded (somehow :) to move the WKT support 
> to proj4 and deprecate the OGR side, thereby maintaining a single point 
> of maintenance, but having that point be proj4?

Paul,

There are rare circumstances where the OGRSpatialReference WKT support is
used without any relationship to PROJ.4, including within FME to implement
their WKT support.  Also I have had at least one client substitute in a
different projections library in place of PROJ.4.  Also, GDAL and related
tools can provide reasonable coordinate system descriptions now even if
PROJ.4 is not installed.

Based on that, I am hesitant to try and restructure everything to put the
OGRSpatialReference WKT logic all down in PROJ.4.  Keep in mind that WKT
is substantially more expressive than PROJ.4 format.

There is also some interest from an influential member of the PROJ.4
community to avoid dumping alot of extra complexity into PROJ.4.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent