[gdal-dev] Re: srs definition for wgs84

[Peter J Halls]

Jukka,

Jukka Rahkonen wrote:
> Peter J Halls <P.Halls <at> york.ac.uk> writes:
> 
>> Imran,
>>
>>     the Oracle SRID value of 8192 *is* WGS84.  Oracle does not store the EPSG 
>> values, but has its own set.  
> 
> Starting from Oracle 10g or something it supports also EPSG codes. Old codes are
> still supported by Oracle but other programs usually do not understand Oracle
> SRID codes. Fortunately they are no more needed. But I think that the correct

    from the (11g) Oracle Spatial reference manual:

"The Oracle Spatial coordinate system support is based on, but is not always 
identical to, the European Petroleum Survey Group (EPSG) data model and dataset."

Methods are provided to express the Oracle SRID as EPSG WKT and to translate 
between Oracle SRID values and EPSG values.  These are needed for programs which 
do not understand the Oracle SRID values.

This means that, without care, Oracle reports will specify the Oracle SRID 
values, which are those stored and used internally, rather than the EPSG values. 
  Oracle also supports projections additional to the EPSG schema.  This seems to 
be what Imran saw.

Yes, this change was introduced at 10g and replaced something rather different 
(and which I have never used), but the current system does not simply use EPSG 
as you imply.

> way to give target SRID with ogr Oracle driver is not to use -a_srs but the
> Layer Creation Option -lco SRID=4326.

Agreed, although up to and including GDAL 1.6.n I have failed to get this method 
to work when using the API.  The problem is more than likely something I've done 
wrong and I have not yet tried 1.7.n.

Best wishes,

Peter

> 
> -Jukka Rahkonen-
> 
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Peter J Halls, GIS Advisor, University of York
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