Bouguer anomaly

In geodesy, the Bouguer anomaly is computed from a free-air anomaly by computationally removing from it the attraction of the terrain, the Bouguer reduction.

In case the terrain attraction is removed precisely, we speak of a refined Bouguer reduction. In case the terrain is approximated by a flat plate of thickness , the height of the gravity measurement location above sea level, we speak of a simple Bouguer reduction. The difference between the two, the differential gravitational effect of the unevenness of the terrain, is called the terrain effect. It is always negative.