  A resolving set for a graph $\Gamma$ is a collection of vertices $S$, chosen
so that for each vertex $v$, the list of distances from $v$ to the members of
$S$ uniquely specifies $v$. The metric dimension $\mu(\Gamma)$ is the smallest
size of a resolving set for $\Gamma$. We consider the metric dimension of two
families of incidence graphs: incidence graphs of symmetric designs, and
incidence graphs of symmetric transversal designs (i.e. symmetric nets). These
graphs are the bipartite distance-regular graphs of diameter $3$, and the
bipartite, antipodal distance-regular graphs of diameter $4$, respectively. In
each case, we use the probabilistic method in the manner used by Babai to
obtain bounds on the metric dimension of strongly regular graphs, and are able
to show that $\mu(\Gamma)=O(\sqrt{n}\log n)$ (where $n$ is the number of
vertices).
