The tomography method described in the preceding chapter
is suited for a particular class of problem.  Using rays
and picking reflectors requires  the dataset
to be relatively clean with strong, fairly continuous reflectors.
Formulating the tomography in tau is universally advantageous,
but shows the most significant improvement over conventional
techniques when velocity is not monotonically increasing.
Finally, in the North Sea velocity general follows structural
dip,  making a steering filter an effective regularization
operator.
%
%I will begin by  describing
%how I built the steering filter operator and some of the issues involved
%in dealing with complex structure.  I will then move onto applying
%the tomography technique to the dataset.  
