“…Besides the obvious advantage of reducing the number of parameters to be determined by eliminating the linear parameters, it has been shown [30,33,22,24] that the resulting reduced problem is better conditioned than the original full one, and if the same optimization algorithm is used it always converges in less iterations. Since with a careful implementation, the cost per iteration is about the same, these results and extensive applications as reported in [14] (where a wealth of references can be found) indicate that there is a net gain in using VP over solving the unreduced problem with a conventional non-linear least squares algorithm.…”