[GRASS-dev] proj -l

[Paul Kelly]

Hello Hamish

On Sun, 8 Oct 2006, Hamish wrote:

> Hi,
>
> I just learned of the "proj -l" command from PROJ.4. (post on Proj.4 ml)
>
[...]
>
> Maybe it would be useful in a future auto-gen g.setproj GUI wizard [if
> GRASS moves to "full" use of proj.4].

There was some discussion about this on the PROJ list a while ago when 
someone was trying to tidy up inconsistencies in the proj -lP with a view 
to automatically parsing it for exactly such a purpose: 
http://lists.maptools.org/pipermail/proj/2003-July/000831.html

but it became apparent that the output isn't reliable enough. Gerald 
Evenden's usage paradigm seems to always have been that before formulating 
a set of PROJ parameters the user needs to read the full documentation for 
that particular projection and understand exactly which parameters they 
need. This manifests itself in some interesting ways such as the multiple 
ways to represent an lcc (Lambert Conformal Conic) projection. I'm sure 
there are others but I have to confess I don't really know very much about 
this, apart from the fact that the intention of the -lP output is 
inconsistent with it being automatically parsed. But it may be possible!

As I said before it would be great to make this functionality part of the 
re-worked PROJ.4 library that Frank is proposing to do at some point.

Paul