Fourteen cameras, seven trained on each goalmouth, have been hung up in all 12 World Cup stadiums. The cameras will record 500 images per second, and a computer will digest the frames. Within a second of a ball crossing the line, the referee's special watch will vibrate and flash "GOAL."
End of the debate? It should be. The designer of the system says 2,400 tests have been run in Brazil, without a mistake.
It's also a type of technology that FIFA repeatedly balked at in the past. But the 2010 World Cup changed that when a shot by England's Frank Lampard in the second round against Germany was clearly over the line, but disallowed.
That goal would have tied it 2-2. Instead Germany won 4-1. And that helped end the indecision.
"Most of the time the referee doesn't have the best vantage point for his decision, goal or no goal," said Johannes Holzmuller, who heads a FIFA program that helped implement the technology. "The same applies for normal TV cameras."
