[Gdal-dev] Projection-Problem

[Frank Warmerdam]

Stephan Holl wrote:
> PROJCS["GK Zone 4 (DHDN)",
>     GEOGCS[,
>         DATUM[,
>             SPHEROID["Bessel
> 1841",6377397.155,299.1528128],582.000000,105.000000,414.000000,-1.040000,-0.350000,3.080000,8.300000],
> PRIMEM["Greenwich",0.000000], UNIT["Decimal
> Degree",0.01745329251994330]], PROJECTION["Transverse Mercator"],
>     PARAMETER["Scale_Factor",1.000000],
>     PARAMETER["Central_Meridian",12.000000],
>     PARAMETER["False_Easting",4500000.000000],
>     UNIT["Meter",1.000000000000],
>     AUTHORITY["Oracle","82032"]]

Stephan,

Whew, this is a screwy WKT definition.  Is that really what is stored
in Oracle's WKTEXT field of the MDSYS.CS_SRS table?  What does it look
like there?

The extra unlabelled numbers in the DATUM are presumably TOWGS84
parameters, but improperly labelled.  I haven't noticed this before.

> [Columns follow here]
> 
> 
> Note that the datum-parameter is empty.
> 
> I can "export" the data into shp using ogr2ogr which results in a shape
> with the following proj-information:
> 
> Feature Count: 10584
> Extent: (4452550.890000, 5324953.370000) - (4479484.079834,
> 5345694.049805) Layer SRS WKT:
> PROJCS["GK Zone 4 (DHDN)",
>     GEOGCS[,
>         DATUM["Mean_Sea_Level",
>             SPHEROID["Bessel
> 1841",6377397.155,299.1528128],582.000000,105.000000,414.000000,-1.040000,-0.350000,3.080000,8.300000],
> PRIMEM["Greenwich",0.000000], UNIT["Decimal
> Degree",0.01745329251994330]], PROJECTION["Transverse Mercator"],
>     PARAMETER["Scale_Factor",1.000000],
>     PARAMETER["Central_Meridian",12.000000],
>     PARAMETER["False_Easting",4500000.000000],
>     UNIT["Meter",1.000000000000],
>     AUTHORITY["Oracle","82032"]]
> 
> Here you can see that the Datum now contains "Mean_Sea_Level". When
> inspecting the written .prj-file from the shape I cannot find any entry
> in the datum-parameters like "Mean_Sea_Level".

I have no idea where ogr2ogr would be getting Mean_Sea_Level from.  Hmm,
looking in gdal_datum.csv it is the "zeroth" record.  Perhaps it is
getting picked up from there as some sort of default.

If you can provide me the extract WKTEXT from the MDSYS.CS_SYS table I'll
see if I can improve the handling.

Best regards,
-- 
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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 OSGF, http://osgeo.org