This paper is aimed at proposing a method for the first-time to calculate the resistance-to-ground of a GEM- encased vertical-rod buried in a homogeneous high resistivity soil. The calculation method is based on the current sphere simulation technique along with the concept of images. The current discharged from the rod into the surrounding GEM is simulated by current spheres, whose diameter is the same as that of the rod. The current through the interface separating the GEM from soil is simulated by two sets of equal number of current spheres. Satisfaction of Dirichlet boundary condition at boundary points on the rod surface and normal current-density continuity along with potential equality boundary conditions at boundary points on the interface formulates a set of equations, whose solution determines the currents of simulation-spheres. The sum of sphere-currents simulating the rod is the current discharged from rod for evaluating ground resistance. The calculated ground resistance after nine weeks for a rod encased in GEM of resistivity 3.39 Ω.m and soil with resistivity 1678 Ω.m records a 47.86% reduction compared to the resistance without GEM. On the other hand, the COMSOL and the experiment predict 44.61% and 49.75% reduction in the ground resistance, respectively