\chapter{Non-stationary regularization}
\label{chap:nonstat}

%% Started 03/01/98
%%
%\lefthead{Clapp}
%\righthead{Regularizing with non-stationary PEFs}
%\footer{SEP--103}
%\input{../appendix/macros_act}
%\email{bob@sep.stanford.edu}
%
%\title{Regularizing tomography with non-stationary filters}
%\author{Robert G. Clapp}
%
%\input{../appendix/abs_act}

\section{Introduction}
\input{../appendix/intro_act}

%\section{Background}
%\input{../appendix/regbasic_act}
%\input{../appendix/covar_act}
%\subsection{Steering filters}
%\input{../appendix/steer_act}
%\input{../appendix/build_act}

\section{Discontinuities and steering filters}
\input{../appendix/dis_act}

\section{Estimating a non-stationary filter}
\input{../appendix/est_act}

\section{Missing data}
\input{../appendix/mis_act}

\section{Tomography}
\input{../appendix/tomo_act}

%\section{Conclusions}
%Non-stationary PEFs are an effective interpolator,
%especially when the model has discontinuities, for missing data problems
%and an effective regularizer for tomography problems.
%The weakness of the approach, the requirement that we have field
%to estimate the PEF from, can be turned into a strength by allowing
%a geologist's conception of the velocity to be directly encoded into the
%regularization.
%A more illuminating 
%test of the non-stationary regularization of
%tomography would be on a model with sharp, rather
%%than smooth, boundaries.  
