[Proj] cs2cs's +towgs84 usage

[Jean-Claude REPETTO]

Le 23/04/2010 14:24, Ilumas a écrit :
>
> Anyway, I believe that the behaviour of a certain towgs84 string is easy
> to test with cs2cs itself: just do the transformation to one direction
> (e.g. from WGS84) and convert the resulting coordinates back to the
> original datum using exactly the same parameter string. If the resulting
> coordinates equal to the original ones, no negation is needed. Right?
>
> ilumas

Hi,

I think you are wrong. To check the parameters, you need to know the 
coordinates of at least one point in both datums, and compare them with 
the results of cs2cs.

Jean-Claude