The earth is not a homogeneous media but composed of rock layers with varying degrees of density. The gravity survey measures localized variations in the Earth's gravity field caused by the presence of other subsurface materials of different densities or voids. Differences in the measured gravity fields are extremely small. As a result, accuracy is vital to the success of such surveys. The company employs the world's standard gravimeters; namely, the L&R G-Meters and Scintrix CG-5 instruments. Inverse modeling software programs are employed to process and interpret the gravity.