  We introduce a new algorithm to construct travel time distances between a
point in the interior of a Riemannian manifold and points on the boundary of
the manifold, and describe a numerical implementation of the algorithm. It is
known that the travel time distances for all interior points determine the
Riemannian manifold in a stable manner. We do not assume that there are sources
or receivers in the interior, and use the hyperbolic Neumann-to-Dirichlet map,
or its restriction, as our data. Our algorithm is a variant of the Boundary
Control method, and to our knowledge, this is the first numerical
implementation of the method in a geometric setting.
