Fabio Rocca deserves to be an author of this paper. He originally derived a shot continuation operator for small dips and suggested it as a tool for velocity analysis. I extended the operator to all dips and implemented the ideas in Mathematica and Fortran. Additionally, I thank Martin Karrenbach and Steve Cole for their constructive discussions. Converting Mathematica's Graphics primitives to vplot would have not been possible without Martin Karrenbach's superb shell programming skills.