On the distribution of the spherical contact vector of stationary germ-grain models

We consider a stationary germ-grain model Ξ with convex and compact grains and the distancer(x) fromxε ℝdto Ξ. For almost all pointsxε ℝdthere exists a unique pointp(x) in the boundary of Ξ such thatr(x) is the length of the vectorx-p(x), which is called the spherical contact vector atx. In this paper we relate the distribution of the spherical contact vector to the times it takes a typical boundary point of Ξ to hit another grain if all grains start growing at the same time and at the same speed. The notion of a typical point is made precise by using the generalized curvature measures of Ξ. The result generalizes a well known formula for the Boolean model. Specific examples are discussed in detail.