  Short precession periods like 164d of SS433 can be well determined by
observations of time scales longer or much longer than the precession period.
However, it doesn't work for sources with precession periods of millions of
years. This paper utilizes the particular morphologies of X-shaped sources, so
that the 3 dimension kinematics of lobes can be obtained. Thus, for the first
time, the million-year precession period of X-shaped sources by observer on the
Earth can be determined elegantly: $(6.1\pm 1.5)$Myr, $(1.8\pm 0.5)$Myr, and
$(3.2\pm 1.2)$Myr for 3C52, 3C223.1 and 4C12.03 respectively. The result
naturally explains the asymmetry displayed in the morphology of these sources,
and the effect of propagation time on the diversity of morphologies is well
demonstrated. The precession period may originate from long-term effects of a
binary super-massive black hole system, which is a potential source of
gravitational wave radiation.
