INTRODUCTION

Migration and diffraction operators can be conceived and programmed in two different ways. Let $\vec {\bold t}$ denote data and $\vec {\bold z}$ denote the depth image. We have

$$\begin{eqnarray} \vec {\bold t} &=& \bold H\ \vec {\bold z} \quad\quad {\rm spr... ...\quad\quad {\rm spray\ or\ push\ a\ semiCircle\ into\ the\ output}\end{eqnarray}$$ (1) (2)

The adjoints are

$$\begin{eqnarray} \vec {\bold z} &=& \bold H' \; \vec {\bold t} \quad\quad {\rm ... ...} \quad\quad {\rm sum\ or\ pull\ a\ semiCircle\ from\ the\ input}\end{eqnarray}$$ (3) (4)

Generally we can choose between the two similar operators $\bold H \approx \bold C'$.For modelling we can make $\vec {\bold t}$ from either $\bold H \vec {\bold z}$ or $\bold C' \vec {\bold z}$.For migration we can make $\vec {\bold z}$ from either $\bold C \vec {\bold t}$ or $\bold H' \vec {\bold t}$.