What is "gravity anomaly"

A gravity anomaly is the difference between the observed acceleration of a planet's reaction to gravity and a value predicted from a model. A location with a positive anomaly exhibits more gravity than predicted, while a negative anomaly exhibits a lower value than predicted. The anomaly is the body or effect that causes the deviation from the "ideal" gravity model. Many data corrections must be made to the measured gravity value in order to extract the response of the local anomaly, or local geology, which is typically the goal of applied geophysics.