[GRASS5] conversions and copyrights

[Frank Warmerdam]

Roger Miller wrote:

> Folks,
> 
> I am drafting the code needed for r.proj, v.proj, s.proj and m.proj to 
> convert between nad27 and nad83 data using the nad_init  and nad_cvt  
> routines and data distributed with proj.4A.3.3.


Roger,

A couple of points.

  o PROJ 4.4.5 already does datum shifting, integrated with the reprojection
    operation using the pj_transform() API.  You can use +datum=NAD27 and
    similar directives to enable datum conversion.

  o PROJ 4.4.5 already has support integrated for Canadian NTv1 datum shift
    files in addition to the US NADCON style data.

Rather than re-invent some of this work based on the old proj code, I
would much rather see it all accomplished in a more integrated way in
GRASS 5.1 using PROJ 4.4.5, even if that code base is just adopted into
the GRASS tree as is done now.  Though, given that we are moving to more
modern use of shared libraries and so forth for 5.1 perhaps we could use
PROJ.4 in it's more natural form.

I am prepared to assist substantially with such an effort.

The license agreement you point of is not compatible with redistributing
the grid shift data.  I assume this is the agreement for the NTv2 data.  Is
that right?  Many vendors distribute the NTv1 data which is now freely
redistributable, though it is lower resolution than the NTv2 data.  I think
they are format compatible so users licensing the NTv2 data can download and
replace the NTv1 data.


Best regards,


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