[gdal-dev] TOWGS84 parameter units

[Thomas Gocke]

Hi,

I have a question about the units of the parameters at the TOWGS84 WKT tag respectively OGRSpatialReference::SetTOWGS84(…)

ESRI and ERDAS specify the TOWGS84 rx, ry and rz paramters in radians, whereas GDAL seems to be expecting them in arcseconds.

DHDN for example is defined by ESRI and ERDAS with 
TOWGS84[598.1,73.7,418.2,-9.793000000000001e-007,-2.182e-007,1.19e-005,6.7e-006]
which seems to give a wrong result in GDAL. 
If I change it to
TOWGS84[598.1,73.7,418.2,0.202,0.045,-2.455,6.7]
it looks right.

Is arcseconds the recommended unit and ESRI and ERDAS don’t stick to the convention or should I always recalculate the TOWGS84 parameters and set them manually with OGRSpatialReference::SetTOWGS84(…) ?

Thanks for helping,
Thomas

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