[GRASS-dev] Projection-Problem

GRASS GIS GRASS GIS developer
,
1

Dear lists,

[sorry for crossposting]

I have a strange problem regarding Oracle spatial datasets.

My dataset has the following projection:

Extent: (4452550.890000, 5324953.370000) - (4479484.079834,
5345694.049805) Layer SRS WKT:
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"]]
[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".

Is this the normal behaviour? I am asking, because GRASS segfaults
when using v.in.ogr with location=newloc parameter enabled.

I am using gdal-1.3.1, grass61 from todays CVS.

Currently out of ideas...

Thanks for your help.

Best
  Stephan

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2

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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