[Gdal-dev] bessel to wgs84?

[Kees Krikke]

Hello,

I'm trying to reproject some images from the Dutch RD coordinate system (epsg:28992) that is defined as:

+proj=stere +lat_0=52.15616055555555 +lon_0=5.38763888888889 +k=0.999908 +x_0=155000 +y_0=463000 +ellps=bessel +units=m  +no_defs

to utm zone 31N /wgs84
+proj=utm +zone=31 +datum=wgs84

For the datum shift i guess i need to specify the +towgs argument also with the source coordinate system. (+towgs=565.04,49.91,465.84,-0.409394387,0.35970519561,-1.868491)

I verified these values by running proj.exe and the results are ok.

But if i use these proj4 strings with the gdalwarp -s_srs and -t_srs arguments the resulting images  are not as i expected. It seems that the shift from bessel to wgs84 is not done. 

What do i need to do in order to create images wgs84  from images based on a bessel ellipsoid?

Thanks in advance.

Kees

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