2nd Test: Australia v England at Adelaide Dec 5-9, 2013

[TheParraboy]

How on earth is someone able to propel a ball faster in Perth than in Adelaide or Brisbane? Is the air somehow thinner?

I believe the speed gun is used (or measuring speed) right after the first bounce on the deck after the bowler has delivered the ball, so as Twiz has said, if the Perth deck is harder and greener, it will generate quicker speed after hitting the deck

 

[Twizzle]

if that were the case full tosses would not register yet the one that Shoab bowled to JL that hit him on the wrist on the full was near 158

from what I have read it measures the ave speed from when the ball leaves the hand till it gets to the batsmen

 

[southwalesrabbitoh]

I've read that it measures the speed over the first few metres, so if it bounces it's obviously quite a bit slower than what's shown on TV.