  In principle, the local classification of spacetimes is always possible using
the Cartan-Karlhede algorithm. However, in practice, the process of determining
equivalence of two spacetimes is potentially computationally difficult or not
at all possible. This difficulty will arise whenever the classifying invariants
are either high-degree rational functions or depend on transcendental functions
without standard inverses. In the case that spacetimes admit Killing vectors
with non-trivial orbits, we propose a new set of invariant quantities, called
Killing invariants. These invariants will allow for the sub-classification of
spacetimes admitting the same group of symmetries and will, in principle, be
substantially less complicated than any other known set. We apply this approach
to the class of static spherically symmetric geometries as an illustrative
example.
