  A precise modeling of light trajectories in the solar system on the
sub-micro-arcsecond and nano-arcsecond scale of accuracy requires the metric
tensor of solar system bodies in post-linear approximation. The Multipolar
Post-Minkowskian formalism represents a framework for determining the metric
density in the exterior of a compact source of matter, which can be regarded as
massive solar system body. The knowledge of the metric density, frequently been
called gothic metric, allows to deduce the metric tensor. Some aspects are
considered about how to determine the metric density and the metric tensor from
the field equations of gravity.
