In jammed static packings,diverse photoelastic tests and numerical simulations have shown that particles are organized into a highly heterogeneous structure.The pair correlation function g(r) is an effective tool for studying the structural properties of granular materials.For example,the first peak of g(r)shows the critical properties in the vicinity of the jamming transition.[1,2] Sun and Ji proposed a variant pair correlation function to describe the characteristic lengths and orientations of anisotropic force chains.[3]To quantify positional order,the bond orientation order parameter ~6 can be used to measure the hexagonal registry of nearest neighbors,both locally and globally,depending on whether or not one is accounting for phase information.