If φ and ψ are two continuous real-valued functions defined on a compact topological space X and G is a subgroup of the group of all homeomorphisms of X onto itself, the natural pseudo-distance dG(φ,ψ) is defined as the infimum of L(g) = ‖φ−ψ ◦ g‖∞, as g varies in G. In this paper, we make a first step towards extending the study of this concept to the case of Lie groups, by assuming X = G = S....