With Wembley set to
host not only Belgium this weekend but also one of Fifa's preferred
ball tracking systems, Hawk-Eye, we thought it would be interesting
to take a look at the systems that are hoping to become standard
across major tournaments and leagues around the world.
Hawk-Eye
Hawk-Eye is the name of
both the system and company that uses ball tracking software in order
to predict the trajectory of a ball. The system relies on a number of
cameras that are used to track the path of the ball therefore
creating a 3D image which can be used to show the exact position of
the ball. In tennis for example it is used to show whether the ball
has landed in or not.
More specifically the
system will use six cameras facing the goal at each end of the
stadium in order to triangulate the trajectory of the ball and
determine whether the ball has crossed the line. Each camera records
the action in 106fps which is much greater than commercial TV.
Indeed the higher frames per second should prevent instances of where
a missing frame on a television replay prevents us from being able to
tell whether the ball has in fact cross the line. When determining
the position of the ball Hawk-Eye uses two inputs. It takes
information of the location of the ball from the six cameras along
with the speed of the ball. This information is then processed using
Hawk-Eye's software. The most important aspect of Hawk-Eye's system,
however, is the speed with which it works. Fifa has stipulated that
information must be passed to the referee in under a second . By
sending an encrypted radio message to the referee's watch as soon as
the ball has crossed the line Hawk-Eye is able to meet this
requirement.
GoalRef
More interestingly from
a technology perspective is actually the other goal-line technology
system that is to be trialled in the Denmark vs Australia game on the
same day as the one at Wembley. Developed by the German research and
development institute Fraunhofer IIS and going by the slightly less
catchy name of GoalRef this alternative to Hawk-Eye uses a chip
implanted in the ball itself, along with magnetic fields across the
goal to tell whether the ball has crossed the line. Low intensity
magnetic fields are created by antennas around the goal area. When
the ball crosses the line the chip inside causes a change in the
magnetic field. This information is then analysed by a processing
unit before the information is sent to the referee. In a
demonstration of the technology the signal that the ball has crossed
the line was sent in only a tenth of a second, well below the one
second demand of Fifa.
Which system will
become the norm
Fifa is set to make a
decision on goal-line technology on 2nd July with both
systems expected to be accepted. The Hawk-Eye system is said to cost
around £250,000 to be installed in a stadium whereas GoalRef is
considerably cheaper with only micro-chipped balls, a magnetic field
and a processing unit necessary for implementation. Although in a
sport where players are paid hundreds of thousands a week it is
unlikely that price will have much of an impact on which system is
adopted by the major leagues around the world. A second consideration
over which system should be introduced is the experience for the TV
audience. Broadcasters have seen the how Hawk-Eye has enhanced the
viewing experience of people in both cricket and tennis and will
surely been more excited by the video feedback a camera based system
provides rather than a micro-chip. Whatever system becomes the
standard across the globe it looks like we won't have to put up with
fans' incessant whining about a disallowed goal for too much longer.
Sources
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