[GRASS5] datum shifts

[Bernhard Reiter]

On Fri, Apr 19, 2002 at 02:15:05PM -0700, rgrmill at rt66.com wrote:
> > Shouldn't this be done at GRASS compile time, so to have the
> > right binary tables for the platform?
> > Or will the format change with proj library versions
> > that have the same binary interface?
> 
> Yes, it does need to be done when GRASS is compiled.

We need a Makefile entry for this.
Maybe Glynn can help if you give him the commands?

> > > I think the data tables 
> > > have to go under $GISBASE somewhere.  
> > 
> > That is not hardcoded, though...
> > It providing an option to specify a non-default path a good idea?
> 
> That part that has to be hard coded is the part after $GISBASE, probably 
> "/etc/nad/".  No more than I know now, it looks easier for me to code 
> this if there is no user option.

Usually I do not call a fixed relative path hardcoded... :)

> > > Wherever they do go has to be 
> > > coded into the proj library.
> > 
> > This confuses me a bit, is it an addition to proj then?
> 
> I guess I could be more specific.  A program that uses the nad<->nad 
> conversion in the proj library has to call a function called "nad_init". 
> "nad_init" takes one argument, and that is the fully qualified file name 
> for the data table that it will use for the conversions.  "nad_init" is 
> part of the proj distribution.  

Okay, thus you have to specify it when initialising proj.
No need to "code" it into library itself.

> It looks now like the name should be 
> 'getenv("GISBASE")/etc/nad/<table name>'.  

Sounds reasonable to me.
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