RealType problem

In my application sometimes I display a 2D chart and
sometimes a 3D chart, when for example I display a 2D
chart with :

time = RealType.getRealType("time", SI.second, null);
height = RealType.getRealType("height");

but if after I want to display a 3D chart (in another
procedure and declaring a nex display) with :

domain_tuple=new RealTupleType(latitude,longitude);

It doesn't work, I have a for latitude and longitude a
null value
And it's the same when I display first a 3D and after
a 2D chart


Nouveau : téléphonez moins cher avec Yahoo! Messenger ! Découvez les tarifs 
exceptionnels pour appeler la France et l'international.
Téléchargez sur