Rockfall is a rapid and rather spontaneous natural hazard. It is a natural process that poses problems in many areas downslope from rocky outcrops throughout the world. To predict the potential rockfall threat, it is not only required to estimate the stopping point or the runout of falling rocks, but also to quantify their kinetic energies, passing (or jump) heights, for each point along their fall paths as well as reach probabilities of the rocks. Therefore, a rockfall trajectory study requires the use of a rockfall simulation model to produce a susceptibility map or a hazard map.