[Proj] How to convert a sphere to ellipsoid with correct datum?

Jan Hartmann j.l.h.hartmann at uva.nl
Fri Sep 3 05:52:49 EST 2010

  On 09/02/10 21:15, Hermann Peifer wrote:
> On 02/09/2010 17:17, Jan Hartmann wrote:
>> Yes, that's logical but it just doesn't work. Doing a transformation
>> with Helmert transformation parameters set to 0 and 1 just gives results
>> that are hundreds of meters off.
> As an exercise, I just transformed lat-lon from one ellipsoid to 
> another one by ussing the "Abridged Molodensky transformation" (EPSG 
> dataset coordinate operation method code 9605) which doesn't go the 
> long route (geographic 3D to geocentric + geocentric to geocentric + 
> geocentric to geographic 3D) but uses some sort of shortcut. Using the 
> 3 parameters dX = dY = dZ = O, I ended up with results which are 
> pretty close to those from cs2cs. 1 meter away, perhaps. So I guess 
> your hundreds of meters offset must have other reasons.
That's a good hint. Could you give me the exact commands and data you 
used and their results, so I can adapt them to my situation?


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