  The Classical Coordinate System is geometrical by nature with time being an
external variable. Constructing a classical coordinate system employs a
point-like signal with infinite speed. In Special Relativity Theory the speed
is limited but the signal is a point-like particle (photon). If the oscillatory
nature of light is considered, an event in absolute space is to be
characterized by three coordinates namely, distance, time and phase. The
Galilean transformation equations for space and time coordinates should be
complemented by a third equation that accounts for the phase transformation.
Wave equation remains invariant under such transformation and kinematical
equivalence of inertial reference frames is conserved. Lorentz transforms apply
to wave length and wave period of the exchanged light signal in a dynamic
set-up.
