The geometric diagram is shown in Fig. 10. As shown, the striking distance to
ground does not exist; it is a default condition. That is, any downward leader that
does not meet the arc described by rc will terminate to ground. Thus all stroke angles
are considered, and all are considered equally likely. However, the downward leader
is not permitted to travel below the height of the phase conductor and then travel
upward to the phase conductor. The exposure of the phase conductor is specified by
the arc Dc and therefore