Detecting the ball's velocity with Radar Guns or Speed Guns is similar to measuring the speed of a moving car. 'John Baker' discovered this approach in 1947. The Doppler Effect is used to operate the speed gun. A receiver and a transmitter are included with this Speed Gun.
The Speed Gun is mounted on a tall pillar near the Sight screen and sends radio waves in the direction of the pitch, calculating the speed of any object on the pitch.
Radar Gun, which operates in a similar way to SONAR, uses a mechanism called 'Doppler Shift' to collect the echo of radio waves as the ball passes through the air.
The data from the Speed Gun is fed into image processing software, which distinguishes the ball from other objects on the pitch and displays the ball's speed.
Because it measures the speed of the rotating ball without error, the Radar Gun or Speed Gun calculates the exact speed of the ball.
The Radar Gun measures the speed of the ball as soon as it passes in front of it. This is why, whenever a bowler tosses the ball in a cricket match, the speed of the ball is immediately displayed on the screen.
Radar Guns or Pace Guns were first used in cricket in 1999 to assess the speed of service of players in lawn tennis.