Generally, even if joint distribution has a regularity, the regularity is not uniform from the view of wide area. In order to generate the rock joint disutribution-model, therefore, it is necessary to classify previously the survey area into regions for which statistical properties of distribution characteristics are similar as much as possible. The authors suggest such area-division method in this paper
Furthermore, a joint system is composed of several joint sets, and each joint set has its own distributional character. In this paper the authors also suggest the division method of joint system into several joint sets.