  Given two semistable, non potentially isotrivial elliptic surfaces over a
curve $C$ defined over a field of characteristic zero or finitely generated
over its prime field, we show that any compatible family of effective
isometries of the N{\'e}ron-Severi lattices of the base changed elliptic
surfaces for all finite separable maps $B\to C$ arises from an isomorphism of
the elliptic surfaces. Without the effectivity hypothesis, we show that the two
elliptic surfaces are isomorphic.
  We also determine the group of universal automorphisms of a semistable
elliptic surface. In particular, this includes showing that the
Picard-Lefschetz transformations corresponding to an irreducible component of a
singular fibre, can be extended as universal isometries. In the process, we get
a family of homomorphisms of the affine Weyl group associated to
$\tilde{A}_{n-1}$ to that of $\tilde{A}_{dn-1}$, indexed by natural numbers
$d$, which are closed under composition.

Algebraic Geometry;Number Theory;Representation Theory