Once values for the upper and lower bounds have been determined, they are used as inputs in the inversion process. GRAV3D uses a logarithmic barrier method, directly incorporated in the objective function, to implement bounds on the model during inversion. An equation for the objective function with the barrier term is given in the equation below. This function is minimized for subsequently decreasing values of the  while keeping the regularization parameter () constant. When  reaches zero the resulting model honors the prior information provided.