Fig. 8

Instruction of Annotation Level 3: The left figure illustrates the virtual baseline of the interval, and the right figure shows physical lines that are utilized to create the virtual grid. In the case of Annotation Level 3, the ball landing location was annotated with a horizontal scale ranging from −2 to 2 and a vertical scale ranging from 0 to 5. The moment when the ball hit the shuttlecock launcher was annotated as “Contact’’.