[GRASS5] error in French projection definition

[Moritz Lennert]

Hello,

On the french-speaking list a discussion has been taking place 
concerning the definition of the French NTF datum. Apparently it is not 
correct as datum.table defines it as using clark80, but the definition 
of clark80 in ellipse.table does not correspond exactly to the one used 
by the French geographical institute.

I am quite unknowledgeable both about projections and about the way they 
function in GRASS, especially the interplay between the GRASS 
definitions and the proj definitions. So before I do anything wrong or 
unnecessary:

- Should I change the two files to reflect the correct defintions. 
Mathieu Basille proposes the following changes:

In datum.table :
# Nouvelle Triangulation Française
ntf      "Nouvelle Triangulation Française"      clark80IGN    dx=-168.0 
    dy=-60.0    dz=320.0

In ellipse.table :
# Clarke 1880 IGN
clark80IGN      "Clarke 1880 IGN"               a=6378249.200 
f=1/293.466021294

- Or is this handled by proj ? What is the relation between the two ?

Sorry about the confusion,

Moritz