Gravity Anomaly Maps and The Geoid. The Earth’s gravity field is depicted in two principal ways: gravity anomaly maps and maps of the Earth’s geoid. Gravity anomaly maps (see globe below) show how much the Earth’s actual gravity field differs from the gravity field of a uniform, featureless Earth surface. The anomalies highlight ... Because of the essential irregularity of actual wind generated gravity waves, the finer developments and the refinements of nonlinear theory have to be sacrificed. Linear theories are used in order to employ the principle of superposition to the best advantage.