i don't see the relevance of your question, Hawkeye's only used for lbw isn't it? All they need to do is predict the theoretic trajectory of a solid ball. The fact that simple technology failed the tests applied to it for use in football seems to point to which is the more difficult.
It's easier to see if a football has gone over a line with the naked eye, than it is to see whether a batsmen has been hit in line with the ball (whether it's plum or going down leg or over the stumps), or whether the batsmen has actually nicked it before it's hit the pads or whether it's pad first. All have to be considered in the lbw rule. I'm talking about the slight variations in the rules. My point being there's no point comparing both. In theory, i agree with you that you can't have it in football unless it's properly tested. And it isn't yet.
I don't mind "ball over the line" technology, providing it does not stop the game, and does not require any human judgement of technology (i.e. a fourth official looking at camera angles etc...). If it is just a quick 'goal' message from a computer, then fine. I just really hope this doesn't lead to more technology, e.g. penalty decisions. Or anything that stops the game.
I really don't understand the argument based around stopping the game/stopping the game flowing. The players do that more than anything else in some games, this would potentially remove any of that because there won't be anything to argue over. 2 minutes of players in the refs face, or 15 secs for a definitive decision. Same reason I'd like to see the 4th or 5th officials actually taking part in officiating and helping the ref. That would stop some of the bad play, bad acting or blatant time wasting that goes on.
Perhaps for a human, but not for the technology, hence it's only just become advanced enough. Which confirms my point. The humans have got it right to a higher standards than machines so far.
Imagine the new technology implemented and then a goal to be given even though numerous camera angles clearly show it wasn't over the line
Or there's an in line switch that means it's only ever going to beep for the home side. I was going to say I can't, but very sadly I can believe how easily people have been duped into this toy for armchairs and pundits.
I don't understand why 4th officials don't advise the ref in the same way as linesmen. A couple of weeks ago when a player was obviously tripped up by his own team mate in front of the tunnel and I heard the 4th apologize to Steve Bruce that they had got the decision wrong, but he didn't say anything to the ref and they still got a free kick that could have created a goal scoring opportunity. They are trained in exactly the same way as the ref is so not sure why they never speak up.
15 seconds for a definitive decision? Haha. People debate for hours after games, and still don't come to definitive decisions.
Its not even goal line technology thats the main problem with the officials. Only about 1 'goal' every month or so will be affected. I don't think its that much of an issue.
