Tuesday, 10 June 2014


The new   football season will see the FIFA world cup 2014 trialling goalline technology. How does it work?..........
It happens from time to time in football: thousands of people filling a stadium watch the ball cross the goal line, but the most important of them all – the referee – hasn’t seen it....more.. Those thousands are aggrieved, the goal is not given, and the whole course of a tournament or league competition is not what it might have been.
Or perhaps the referee does award a goal – one that the defending side insists shouldn’t stand. The German language even has a specific term for it: a “Wembley-Tor”, after the goal that gave England a 3-2 lead in the 1966 World Cup final. The story that the “Russian” linesman, actually from Azerbaijan, when asked how he could be so sure that the goal was legitimate, replied simply: “Stalingrad” is probably apocryphal.
Now, technology is being introduced in an attempt to overcome human error with mathematical certainty. The two main systems being trialled are Hawk-Eye and Goalref


   Principles of GLT     

*  GLT applies solely to the goal line and
only to determine whether a goal has
been scored
*  The GLT system must be in accordance
with the FIFA Quality Programme for GLT
* The indication of whether a goal has
been scored must be immediate and
automatically confirmed within one second
The indication of whether a goal has
been scored will be communicated
by the GLT system only to the match
officials (via the referee’s watch, by vibration and visual signal)

How will it work?
There are seven cameras at each end of the stadium focused on the goals. The most common location for the cameras is on the roof of the stadium, however there is a great deal of flexibility in the camera positions. The images from each of the cameras are processed to find the ball within the image and identify areas which are not the ball. They track the ball when it comes into their range and they can tell when the whole of it crosses the goalline. When such an event occurs, within a second the outcome is relayed to the match referee via a watch that Hawk-Eye has exclusively developed with Adeunis. The signal is encrypted and is unaffected by interference.

How accurate is it?
The Hawk-Eye system betters the FIFA margin-of-error requirement of +/-3cm.

What about players obscuring the ball at the moment it crosses the line?
The seven cameras are able to locate accurately the ball even when only a small percentage of it is visible to the cameras and in extensive tests the ball has always been visible enough for an outcome to be decided.

Will television viewers be able to see the judgment made by Hawk-Eye?
Yes, in a similar way to the tennis or cricket, a video replay will be made available of the incident within 10 seconds of it occurring. Hawk-Eye uses a dedicated high speed camera capable of removing the players from the image, to ensure the ball is fully visible. This provides the definitive replay for broadcast and digital media.

What about the fans in the stadium?
  world cup 2014 is looking into making these videos also available at stadiums which have screens that can show them.

Can the elements, such as fog, rain or snow, disrupt the cameras’ view of the goal?
No, the cameras are strong enough to ensure that if visibility is good enough for the officials to allow the match to go ahead it is good enough for them to do their job. Mud on the ball will also not affect the system.

souce: phy.org,fifa news

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