A tape measure is a pretty good way to measure distance. Not perfect, but pretty good. Given the low stakes involved in getting the 50mk line wrong, I reckon we can live with it.
A petrometer is a pretty good way to measure how far a small piece of metal goes into the ground when you drop a 1 kg weight on it.
Sadly, very few players are small pieces of metal with 1 kg weights on them; rather they are 90kg athletes on footy boots running 10kms in a couple of hours. If only there was some way to know how they felt about the ground. Sadly, asking those players whose livelihood depends on the outcome is pretty unscientific, so we should probably rely on the unseen results of a small piece of metal with a 1 kg weight on it being operated by the stadium manager with a vested interest in ensuring the games go ahead.
Because science.
