[GRASS-dev] need update to core.create_location

[Paul Kelly]

Michael Barton wrote:
> Arrgg.
>
> Before Paul's update to g.proj today, it turns out that g.proj would
> actually accept the argument "datum" as equivalent of the argument
> "datatrans", even though this is not in the manual. I don't know if that
> was intentional or an accident. So g.proj datumtrans=1 could also be
> expressed as g.proj datum=1.

The g.proj option has always been called "datumtrans", but GRASS allows 
the user to shorten command-line options by dropping letters off the 
end, as long as they still unambiguously identify the option (and GRASS 
7 extends this a bit further). So beforehand as there was no "datum" 
option, "datum" would have unambiguously identified "datumtrans". Now 
you need to type at least "datumt" in order to distinguish it from the 
new "datum" option.

I think as long as everywhere in GRASS 7 that might use the datumtrans= 
option is updated to use it correctly, there should be no problem. Of 
course we could also call the new option something other than "datum", 
but it seems like such a clear and obvious name that it seems to me a 
pity to have to change it!

One other thing - please don't backport for a few days; if I get time I 
want to try and make an improvement to the code so that the ellipsoid 
will always be changed if the datum is changed. As it is currently, it 
is theoretically possible to change the datum to one that is 
incompatible with the ellipsoid.

Paul