Does somebody know how serve speed and topspin rate are measured in Tennis TV stats ? Traditionally speed has been measured via speed-gun via doppler effect, but I have never seen such device at tennis tournament recently. I guess Hawk-Eye can track 3D and measure the (initial) serve speed as well as how much the ball is spinning ?
I think I've read somewhere sometime that radar is still used for live serve speed display at the court. But Hawk Eye is much more sophisticated system that uses multiple cameras for ball tracking which is then transformed in 3D path vector from which it is possible to extract speed and trajectory data at arbitrary point on the path. Spin rate though, I believe is probably extracted from the video from cameras, knowing the video frame rate.