  In this paper (Part I of a series of three papers) an axiomatic formulation
of GR is given, here use is made of the concept of pre-radar charts. These
charts have "infinitesimally" the same properties as the true radar charts used
in space-time theory. Their existence in GR has far-reaching consequences which
are discussed throughout the papers. For the sake of simplicity and convenience
I consider only such material systems the state of which is defined by a
velocity field, a mass density and a temperature field. But the main results
hold also for more complex systems. It follows from the axiomatics that the
pre-radar charts define an atlas for the space-time manifold and that, in
addition, they generate the metric, the velocity field and the displacement of
the matter. Therefore, they are called generating functions. They act like
"potentials". At the end of the paper it is shown that the existence of
pre-radar charts allows to simplify the original axiomatics drasticly. But the
two versions of GR are equivalent.
