Editing Instant replay (section)

===Tennis===
{{See also|Hawk-Eye|MacCAM}}
[[File:Hawk-Eye at Wimbledon (7508887344).jpg|thumb|Hawk-Eye in use at Wimbledon.]]
In [[tennis]], systems such as Hawk-Eye and MacCAM calculate the trajectory of the ball by [[Image processing|processing the input]] of several video cameras. They can play a [[computer graphics|computer rendering]] of the path and determine whether the ball landed in or out. Players can appeal to have the system's calculation used to override a disputed call by the umpire. In March 2008, the [[International Tennis Federation]], [[Association of Tennis Professionals]], [[Women's Tennis Association]] and [[Grand Slam (tennis)|Grand Slam]] Committee agreed unified challenge rules: a player can make up to three unsuccessful challenges per set, and a fourth in a [[tie-break]].<ref>
{{cite news |url=http://news.bbc.co.uk/sport2/hi/tennis/7305404.stm |title=Hawk-Eye challenge rules unified |date=19 March 2008 |publisher=BBC|access-date=29 November 2009}}
</ref> Television broadcasts may use the footage to replay points even when not challenged by a player.