Watching the 2013 Australia Vs England Test series ("The Ashes"), I have seen for the first time an interesting piece of technology which shows the rotation speed of the ball. This is used when spinners are bowling, to give viewers an idea how much each ball is spinning (so you can see if it was an arm ball, stock ball, big turner etc). This is called the 'rev counter'.

Does anyone know, preferably with a reference, what technology this is based on? I would presume some kind of microwave doppler radar, but it seems like a very tricky thing to implement. I don't think it is a high speed camera as the results are obtained almost instantly once the delivery is bowled (as per the speed camera results, which do use a microwave doppler radar).

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    I was just about to have my sleeping question on Physics SE migrated here (and now won't), so: Thanks for asking! (See physics.stackexchange.com/q/70600/17609.)
    – user1564
    Commented Jul 23, 2013 at 16:18
  • Maybe they use something like this ("3D Doppler radar"). Also see trackman.dk .
    – user1564
    Commented Aug 9, 2013 at 21:51
  • @user1564, it's highly likely that your first link is on the money, particularly if this type of system is already in use at baseball fields, which would pose comparable challenges to setting it up to monitor a cricket game. The key is to have multiple radars. I couldn't figure out how you could do it with one (you'd just get the same info as the conventional speed gun) but with multiple radars it seems plausible. Difficult, but plausible. Commented Aug 12, 2013 at 0:48
  • I wish I knew the answer....but wonder if they're using some sort of Doppler radar system so can measure the speeds of approach/recession of the edges of the ball and calculate the speed....unless some form of 'edge detection' uses the seam to count revs? Anyone know for sure?
    – user4823
    Commented Jun 21, 2014 at 13:51

2 Answers 2


As there is no official wording from Sky Sports on technology behind Rev Counter there were two possible theories, one would be high-speed camera coupled to a computer running an image recognition/analysis program as mentioned in the Physics StackExchange Question. Which would be challenging in that given time frame.

Other one is 3D Doppler Tracking that is used in products developed by company FlightScope to measure Golf Ball data, which can be used to measure variables like ball speed, spin rate, spin axis, and many more.
    As they have mentioned in this Company link about the use of their technology in Cricket Ball Tracking. Their product may be the used technology.

The principles of the 3D Doppler Tracking, and How does the 3D Doppler Tracking Radar work? can be viewed in this Link to site and this Link for working example.


Ball Spin RPM - Starting during the TV coverage by Sky sports for the 2013 Ashes series, they were able to show a RPM (revolutions per minute) counter, showing how fast the ball was spinning after release. It is not clear how this is measured, though it would need a high speed camera focussed on the ball, possibly using the same images that are captured for the Hawkeye system.

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