[OSRS-PROJ] Datum Shifting

[Morten Hulden]

Frank,

On Tue, 4 Jul 2000, Frank Warmerdam wrote:

> As I understand it the current ``proj'' command only allows conversion between
> a single projected coordinate system and geodetic (lat/long) coordinates on
> the same ellipsoid.  In particular, there is no way to convert directly from
> one projection to another since it is assume that all projection definition
> information on the commandline relates to one definition. 

ob_trans projection allows a second projection to be specified e.g. (a
pole shift)

proj +ellps=clrk66 proj=ob_trans +lon_0=20 +o_proj=tmerc o_lon_p=45

but, you are correct, not a second ellipsoid
and anyway I think your approach is cleaner:

> proj +proj=utm +zone=11 +ellps=clrk80 -to +proj=utm +zone=11 +ellpse=GRS80


Morten Hulden

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