We now use Conjugate Gradient method for WET inversion, as an alternative to our default Steepest Descent method. See

http://rayfract.com/help/release_notes.pdf

for latest version 3.31 and

http://www.cs.cmu.edu/%7Equake-papers/painless-conjugate-gradient.pdf

on Conjugate Gradient theory.

Also, we now allow Gaussian weighting for smoothing instead of uniform weighting, for improved resolution.