Great Circle Plots on Arbitrary Maps

Mathematical methods are presented for obtaining the locus of points representing the intersection of the figure of the earth and the plane defined by the central ray of a signal scattered between two sites. Algebraic expressions of the latitude-longitude pairs which represent the locus are presented for the case where the figure of the earth is a sphere. An outline of the method for determining latitude-longitude pairs is included for the case where the figure of the earth is an oblate spheroid.