function [l,u]  = observe( T,X,P )
% function [l,u]  = observe( T,X,P )
u = [];
for i=1:size(T,2);
   for j=1:size(X,2);

      x = P{j}*T{i}*X{j};
      x = x/x(end);
      l{i,j} = null(x')'*P{j};
      u = [ u  [j;i;j;x]] ;
   end;
end;