  We show how a suitably prepared set of clocks can be used to determine all
components of the gravitational field in General Relativity. We call such an
experimental setup a clock compass, in analogy to the usual gravitational
compass. Particular attention is paid to the construction of the underlying
reference frame. Conceptual differences between the clock compass and the
standard gravitational compass, which is based on the measurement of the mutual
accelerations between the constituents of a swarm of test bodies, are
highlighted. Our results are of direct operational relevance for the setup of
networks of clocks, for example in the context of relativistic geodesy.
