[GRASS-user] r.proj's "use different location" error while working in different dbases

[Nikos Alexandris]

Nikos Alexandris wrote:

> > Alternative solution with respect to the specific example here: allow
> > g.copy to copy data from another dbase/location to the current dbase in
> > a location with identical name and projection definition of course (?).


Glynn Clements:

> We don't currently have any way to check whether two projections are
> identical, and this isn't a trivial question. E.g.:
> 
> 1. Some of the parameters are floating-point values, so we would need
> to choose some kind of tolerance.
> 
> 2. Are WGS84 and NAD83 the same? In the absence of grid shift files,
> the only difference is that the eccentricity of the WGS84 and GRS80
> ellipsoids differ by 1.5e-6.
> 
> 3. If the projections use grid shift files, do we just check that they
> use the same file, or do we compare their contents?


Seems not that easy after all. As a simple user I would expect that (at
least?) locations created using 'epsg:4326' would be easy to
compare/identify.

Nikos