The practical aspects of data regularization by iterative optimization
are discussed in Chapter . Considering two possible
formulations of the optimization problem, I show that the data-space
formulation (also known as model preconditioning) provides
significantly faster convergence and exhibits more appropriate
behavior at early iterations than the alternative, model-space
formulation. I introduce preconditioning by recursive filtering and
apply it in multidimensional problems with the help of Claerbout's
helix transform Claerbout (1998a).