I'd think that pace and spin could be extrapolated relatively easily if you know placement and time; particularly if you know (or can extrapolate) the height of

I'd think that pace and spin could be extrapolated relatively easily if you know placement and time; particularly if you know (or can extrapolate) the height of the ball. edit: Well, perhaps not entirely. Trajectory is a function of a number of factors including spin. However, the ball itself is a factor. More fuzz = more drag = spin has a greater effect on trajectory. That would vary from ball to ball and even over the lifetime of an individual ball. -- For those not familiar with tennis: Primarily because of aerodynamic drag created by the fuzz on tennis balls, the ball's spin greatly affects its trajectory. A topspin makes the ball dive down more sharply. This is how players can hit the ball extremely hard and fast, yet still land in bounds, as opposed to flying out of bounds. This "trick" of topspin is also why tennis is easier than it may first seem if you've ever tried it. It's not easy to learn topspin but once you do, it increases your margin for error.