[Gdal-dev] Grid based transformation with ogr2ogr

[uwe.schmitz at lverma.nrw.de]

Frank,

> Uwe,
> 
> I must appologising for not noticing/commenting on another issue.  If
> you expand +init=epsg:31467 it looks like:
> 
>    +proj=tmerc +lat_0=0 +lon_0=9 +k=1.000000 +x_0=3500000 +y_0=0
>       +ellps=bessel +datum=potsdam +units=m +no_defs
> 
> The +no_defs part actually means no defaults, but it is implemented
> by ignoring all items that come after it.  So I believe that the
> +towgs84= clause is being ignored by one or both of ogr2ogr and
> cs2cs.  To ensure you control the settings you should provide the
> definition directly instead of using the +init mechanism.
> 
> eg.
>     +proj=tmerc +lat_0=0 +lon_0=9 +k=1.000000 +x_0=3500000 +y_0=0
>       +ellps=bessel +towgs84=631,23,451 +units=m +no_defs
> 
> I also discovered that you do *not* want to use +datum=potsdam or
> else the internal PROJ.4 towgs84 definition for potsdam will 
> take over.
> 
> I must confess this stuff isn't as obvious as it ought to be!
> 

Ok, now it works as expected! Our discussion clarifies
some things for me.

Many thanks for your help!
Uwe