Now that we have set up our tomography problem it is time to test the
theory and compare the advantage of depth vs. tau tomography. 
The model, Figure~\ref{fig:synth-model},
is a  difficult challenge for tomography, especially ray based
tomography. Our linerazation approximation works best
when we are close to the
correct model.  In this case we are up to $1 km/s$ off in places.
In ray tomography we
assume that are raypaths are generally correct.  With this model our
initial  reflector positions are in significant error.
As a result we can't expect to get a satisfactory result after a single
itteration of tomography, and there is a chance that
we will quickly fall into a local minima and not be able to converge to
a satisfactory model.
\par
Figure~\ref{fig:res.vel0} is the result of migrating with the $v(z)$ velocity
away from the anticline
with the correct reflector positions indicated
with `*'.
As expected away from the anticline our gathers are flat
and we have correctly positioned our reflectors.  Along the edge
of the anticline we see upward curvature in our CRP gathers showing
that we have used too slow of a velocity at this location.  Below
the center of the anticline, $x=10$, the bottom reflector shows some reverse
moveout, the well known $W$ pattern, better illustrated 
in Figure~\ref{fig:semb-mig0-ref}.

\plot{res.vel0}{height=3.0in, width=6.0in} {Our initial migration result
using a $v(z)$ velocity function from the edge of the anomaly. Note that
the CRP gather at $5.5$ is flat while the other two CRP gathers show 
significant moveout.}

\subsection{First itteration}
\sepinput{first}

%\subsection{Line search}
%\sepinput{huber}

\subsection{Three itterations}
\sepinput{best}