That wouldn't help in the slightest. For one the ball doesn't follow a perfect, straight, horizontal path as it is passed. Secondly the cameras would still be unable to distinguish where the ball is relative to these lines, and thirdly (and most importantly), the ball can travel forward relative to the pitch.

Apart from the fact that one decision is based on the absolute position of the players and the ball and the other is based on the relative position of the players and the ball, you are right, they are exactly the same

Good quality ones are. They use them in geology to measure land movement of millimetres over long periods of time.

No I said the system you proposed wouldnt be possible. To avoid confusion i mentioned Hawkeye the company, not hawkeye the system.

Even for you Smokey, that's a poor attempt to wriggle out of something you've said!

Its not really complex to say there may be an engineering solution for accurate judgement of forward passes, but your's wasnt it.