[GRASS5] datum shifts

[Glynn Clements]

Bernhard Reiter 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?

Sure.

> > > > 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.

FWIW, the "official" mechanism is G_gisbase(), e.g.

	sprintf(pathname, "%s/etc/nad/%s", G_gisbase(), table_name);

-- 
Glynn Clements <glynn.clements at virgin.net>