Explainer - Why the BCCI changed its stance on DRS

Despite winning the 2011 World Cup and the 2013 Champions Trophy with DRS in place, India had resisted using the system in bilateral series. On Wednesday the ICC general manager Geoff Allardice and a representative from Hawk-Eye, the ball-tracking technology provider, met top BCCI officials along with India coach Anil Kumble in Delhi.

Allardice focused on the independent assessment of the technologies used in the DRS, which was carried out by engineers from the field-intelligence unit at the Massachusetts Institute of Technology [MIT]. The Hawk-Eye presentation explained how ball-tracking technology has been enhanced over the last couple of years.

The upshot of the meeting was that two days later India agreed to use the DRS on a trial basis during the Test series against England. Here's an explainer of what their concerns were and how they were allayed.

Why did the BCCI not want the DRS?
The main reason was a mistrust of the ball-tracking technology used to adjudge lbws. The BCCI said the predicted path after the ball hit the pad was not reliable.

How does ball-tracking work?
Three elements go into an lbw decision: where the ball pitched, the point of impact on the pad, and the predicted path towards the stumps. The accuracy of the predicted path of the ball depends on the number of images captured - the frame-rate - between the ball pitching and hitting the pad.

What is the most significant change in the technology?
Cameras with a higher frame rate, and the ability to locate the point of impact on the pad more accurately.

How fast are the frame rates now?
During the 2011 World Cup, the frame rate of Hawk-Eye's cameras was 50 to 75 frames per second. Hawk-Eye's ultra-motion cameras recorded images at a faster rate in 2013, and their current ball-tracking cameras record images at 340 frames per second.

How will a higher frame rate help?  It provides a lot more data and hence the calculation of the predicted path of the ball is more accurate. "The increased frame rate has allowed the accuracy of the prediction to tighten up significantly," an official privy to Wednesday's presentation said. "It means between the ball pitching and the ball hitting the pad there is more information available to go into building a prediction. That was something reinforced by the recent testing of the accuracy of a prediction, when compared to the accuracy of a ball that has not been intercepted."

Why did the BCCI have an issue with the location of the point of impact?
When judging the point where the ball hits the pad, a key factor is to make sure the ball has not changed path. The BCCI had said there was potential for operator error while identifying the point of impact.

How was that issue solved?
Hawk-Eye created Ultra Edge to remove that problem. Ultra Edge is a sound based, edge-detection system can identify the point of impact more accurately. When there is a sound of ball hitting pad or bat, it can identify the frame in which the ball hits the pad.

What if the operator misses the ball? How will they locate point of impact?
Hawk-Eye has added another safeguard to its system: data from every delivery is recorded and can be retrieved in case it's needed to build a predicted path of the delivery.