  Transfer matrix methods and intersection theory are used to calculate the
bands of edge states for a wide class of periodic two-dimensional tight-binding
models including a sublattice and spin degree of freedom. This allows to define
topological invariants by considering the associated Bott-Maslov indices which
can be easily calculated numerically. For time-reversal symmetric systems in
the symplectic universality class this leads to a Z_2-invariant for the edge
states. It is shown that the edge state invariants are related to Chern numbers
of the bulk systems and also to (spin) edge currents, in the spirit of the
theory of topological insulators.
