This paper presents some models of markings and thinnings of Poisson p
rocesses. Examples of marks are distances and directions to nearest ne
ighbours. The concept of the mark variogram is introduced. Using a sim
ple relation between thinned Poisson processes, the second-order produ
ct density of that cluster process is given which is complementary to
Matern's hard core process. An example shows that it is of value for s
patial statistics.