When dip and offset are combined, some serious complications arise. For many years it was common industry practice to ignore these complications and to handle dip and offset separately. Thus offset was handled by velocity analysis, normal moveout and stack (chapter ). And dip was handled by zero-offset migration after stack (chapters and ). This practice is a good approximation only when the dips on the section are small. We need to handle large offset angles at the same time we handle large dip angles at the same time we are estimating rock velocity. It is confusing! Here we see the important steps of bootstrapping yourself towards both the velocity and the image.