[R-sig-Debian] r-cran-rgdal: dependency on libgdal1 unsatisfied in ubuntu 12.04?

[Matthieu]

Hi

I am trying to install the rgdal package through r-cran-rgdal (I had 
added the ppa), and run into an error in Ubuntu 12.04:
r-cran-rgdal : Dépend: libgdal1 (>= 1.9.0) mais il n'est pas installable

in English, libgdal1 1.9 does not seem available in Ubuntu 12.04 (I 
think version 1.7) comes.

And indeed, a:
$sudo apt-get install  libgdal1

Gives also an error message, saying libgdal1 not available, but 
suggesting libgdal1h, although installing the latter does not solve 
anything.

I looked into several forums, tried to install from several  ppas, but 
was not able to get it working. Would someone have an idea how to 
install this unsatisfied dependency?

Thanks!

Matthieu