[Proj] puzzled with +towgs84=... being ignored

Andre Joost andre+joost at nurfuerspam.de
Fri Jan 10 10:13:39 EST 2014

Am 10.01.2014 11:54, schrieb Just van den Broecke:
> Hi,
> I agree with Andre. One remark. Looking at the parameters, I presume you
> try to transform to Dutch, EPSG:28992. Your +towgs84 parms seem have an
> "unusual" value, maybe outdated, or perhaps on purpose. The others are ok.
> Your value:
> +towgs84=593.0297,26.0038,478.7534,0.40685733032239757,-0.3507326765425626,1.8703473836067959,4.0812
> Proj 4.8.0 value:
> +towgs84=565.417,50.3319,465.552,-0.398957,0.343988,-1.8774,4.0725 (see
> <28992>  entry in http://trac.osgeo.org/proj/browser/trunk/proj/nad/epsg)

The 565.417,... is the correct one. The other parameter set is for 
rotation around Amersfoort instead of the ellipsoid center as used by Proj.

See http://trac.osgeo.org/geotiff/ticket/22 and the attached excel sheet 
supplied by Jan Hartmann evaluating the different parameter sets.

André Joost

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