[MetaCRS] Oracle WKT

[Norm Olsen]

Hello Frank . . .

Yes, Oracle 10 is significantly different from Oracle 9.  Never seen an Oracle 8, I don't think.  Could you send me some samples?

Most all of these issues have been addressed in CS-MAP.  Off the top of my head, the issues are:

1> The names of the definitions are all different, and most now include an EPSG reference.  This can be helpful, but cannot be relied upon.

2> The PROJECTION element now rarely contains the name of a projection, but has a reference to an EPSG Coordinate System Operation definition.  This is not the EPSG Operation _Method_ code, it is an EPSG Coordinate _Operation_ code.  A table which mapped the EPSG Operation Code to a projection was built to CS-MAP to handle this.  Of course, this is a maintenance nightmare.

3> In some cases, there are no PARAMETER elements for the coordinate system definition.  Presumably, having the EPSG Coordinate Operation Code you can get the parameter values from the EPSG database.  Perhaps for Oracle this is a piece of cake; not so for us mere mortals.

4> Oracle 10 will now often include datum transformation parameters, but without the benefit of the TOWGS84 element.  Of course, this presents all the problems associated with the TOWGS84 element.  Code that parses the DATUM element will need to be able to handle these extra seven parameter values appropriately.  (I think there are always seven, my memory could be wrong.)

5> Many numerical values are given to 20 or so decimal places; could cause problems with some parsers.

Handling Oracle 10 was your typical WKT pain in the posterior problem.  Distinguishing between 9 and 10 is also tricky, which we needed to do.  My condolences to whomever has to do this.  I am available for consultation and, perhaps more importantly, consolation and commiseration.

Norm

-----Original Message-----
From: metacrs-bounces at lists.osgeo.org [mailto:metacrs-bounces at lists.osgeo.org] On Behalf Of Frank Warmerdam (External)
Sent: Thursday, July 24, 2008 12:39 PM
To: metacrs at lists.osgeo.org
Subject: [MetaCRS] Oracle WKT

Folks,

Mateusz Loskot is currently working on improved support for Oracle
coordinate systems in the OGR Oracle Spatial driver.  I'm wondering
if others here have experience with Oracle WKT coordinate system
definitions - possibly with suggestion on how to map them to more "OGC
standard" format.

Also, it seems the WKT is quite different between Oracle 9 and 10.  We
haven't tried to compare to 8.  Does anyone have advice on how to handle
things for different Oracle versions?

We are anticipating implementing morphToOracle() and morphFromOracle()
methods in the OGRSpatialReference class, similar to what we have done in
the past to map between OGR WKT and ESRI WKT.

Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org

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