The inversion of the cross-product matrix is a computationally
challenging task. We use an iterative solution to estimate the inverse
of . This solves a huge set of simultaneous equations without
the need to write down the matrix of coefficients.
The iterative technique is based on the conjugate gradient
method, which produces a good result at a reasonable cost. Experience has shown
that a satisfactory solution for equation (11) can be achieved
in less than 10 iterations,
where each iteration involves the application
of the adjoint followed by the forward operator. In every
iteration, a total of 2*n* AMO operations are performed
in order to project each
trace to all the other traces in the selected input.
Note that both the forward and transpose operations are AMO transformations.
The cost of each operation is very cheap giving the narrow
aperture of AMO.

11/11/1997