[Proj] NZGD2000 to NZGD49

[Anthony Dunk]

Hi Simon,

I think the problem is that NZ datums are not defined in PROJ (I found
the same was true of Australian datums). You will need to provide the
ellipsoid parameters for these datums instead. i.e. +a=6378388.0
+rf=297.0 for NZGD49 and +a=6378137.0 +rf=298.257222 for NZGD2000.

So, to convert from NZGD200 Lat/Lon to NZGD49 Lat/Lon try this:

cs2cs +proj=latlong +a=6378137.0 +rf=298.257222 +to +proj=latlong
+a=6378388.0 +rf=297.0 +nadgrids=nzgd2kgrid0005 

Anthony.

--- Simon O'Malley <simonom at gmail.com> wrote:

> Hi
> 
> I am trying to test the datum shift (using nzgd2kgrid0005.gsb file)
> for
> conversions between NZGD2000 and NZGD49(NZMG).
> 
> I have downloaded the proj-datumgrid-1.3.zip file, and extracted
> everything
> under the nad directory.
> 
> configured, make, and make install. However the gsb file does not get
> copied
> to /usr/local/share/proj
> 
> I copied it across but postgis does not appear to use it i.e. my
> transformed
> coordinates are not correct, as verified by the linz website and
> other
> software that uses the grid file.
> 
> I then tried to use cs2cs to validate it but all attempts at
> specifying the
> projections and datums gave me errors.
> 
> I have tried multiple versions of:
> 
> cs2cs +proj=latlong +datum=nzgd2000 +nadgrids=nzgd2kgrid0005 +to
> +proj=nzmg
> +datum=nzgd49
> 
> After setting PROJ_DEBUG I get:
> 
> pj_open_lib(proj_def.dat): call
> fopen(/usr/local/share/proj/proj_def.dat) -
> succeeded
> Using from definition: proj=latlong datum=nzgd2000
> nadgrids=nzgd2kgrid0005
> Rel. 4.4.9, 29 Oct 2004
> <cs2cs>:
> projection initialization failure
> cause: unknown elliptical parameter name
> program abnormally terminated
> 
> Tried upper and lower case NZGD2000, NZGD49, NZMG, latlong, longlat,
> without
> nadgrids???
> Do I have to add an ellipsoid to the projection definitions for
> cs2cs?
> 
> The grid shift file does not appear to mentioned in any of the files
> in
> /usr/local/share/proj is that normal?
> 
> Some pointers would be appreciated.
> 
> Simon
> > _______________________________________________
> Proj mailing list
> Proj at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/proj




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