A computer program is described for use on the IBM-704/7090 electronic data processing machine or any large computer accepting FORTRAN. The necessary modifications for use on these two computers are simple and self-evident. The computer program permits the computation of detailed ray patterns portraying the spatial distribution of rays emitted from a transmitter whose geographic coordinates with respect to the center of the earth are known. This program deals with the solution of the differential equations, given by Hamiltonian optics, for ray paths in non-isotropic, three-dimensionally non homogeneous media whose complex phase refractive index is given by the Appleton-Hartree formula. An account of the current status of the development of this program, which has yielded many useful results is presented. Sample calculations as well as some results that were obtained by using this program are also presented.