[GRASS5] datum shifts

[rgrmill at rt66.com]

> It is hard for me to judge if this might be a cause for more bugs 
> or can be savely done. 
> We have the possibility to schedule this addition for 5.0.1
> depending on the answer.

The changes in the user modules are fairly small, so I don't anticipate 
this will spin off a lot of new bugs.  But then, I'm an optimist.

Installation bugs are another matter.  I don't know much at all about 
configure or make, so someone else will have to estimate the chance of 
introducing installation bugs.


> What does " They have to be interpreted to binary by a program" mean?

The tables are delivered in plain text.  The proj library functions read 
them in a binary format.  There is a program in the proj-4.4.5 library 
called nad2bin that performs the function of reading the ascii tables 
and rewriting them in the format that the library functions need.  That 
will have to be taken care of during GRASS installation.  After 
installation the nad2bin code is only necessary if the tables are later 
updated.

> > The user modules must know where the data tables are stored, and 
that 
> > information should be compiled into the modules.  I think that would 
be 
> > done by configure, but I don't know enough to say, much less enough 
to 
> > make the change myself.
> 
> Is there a possibility to make this relative to 
> an environment variable the GRASS installation is using anyway?
> We should not have fixed paths compiled in that prohibit that
> the GRASS installation can be moved. So I guess relative to other
> GRASS files should be fine. Maybe you don't even need configure for 
this.

If $GISBASE is still exported by Init.sh then it would be possible to 
place them in $GISBASE/lib/nad for instance.  I think the data tables 
have to go under $GISBASE somewhere.  Wherever they do go has to be 
coded into the proj library.


Roger 


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