To calculate GPS accuracy you use a military balistics measurement called 'circular error probable', or CEP. What a CEP does is factor in that the chances of hitting are target directly are severely minimal, so you create a circular distance from zero hit point, if it hits with 50% of your circular distace from point zero its considered accurate. The CEP of a GPS means you get a "correct reading" within a 2 metre radius.
For those who don't believe me, as obviously I'm not an expert, here is a quote from a mathematical study into GPS accuracy entitled 'GPS Accuracy: Truths and Myths in the Maths' done by an American Road data and management company in which they sampled common road GPS and high end military tech:
"One of the more common "gotchas" in describing GPS accuracy is the occupation time required to achieve the claimed accuracy. Be wary if the device does not explicitly state how long you must occupy a location in order to achieve a particular accuracy. In the best case scenario, the required occupation time might be as little as one second. However, several systems that tout sub-meter accuracy are only able to achieve this after a stationary occupation of at least several minutes."
In the case of a football game where the ball is in constant movement in a running player's hands, then quickly changes directions in a fraction of a second as it is passed to another player I will never trust it and don't think it should be implemented. I'm not against technology upgrades for the game, but this one just doesn't stack up for me. The technology isn't sofisticated enough.
