Estimating Distance Travelled by Ball using 2 Cameras

Hi All,

I need to estimate the distance travelled by the ball. I am able to track the ball trajectory using 2 cameras and I also have the location of both the cameras and goal post. Please find the attachment of the video and camera distance.

I am able to track the ball trajectory in all cameras. Can anyone please suggest me for the approach for estimating the distance travelled by the ball.

Vishal Chauhan

When you say distance, do you mean the path length of the ball as it flies through the air, or the resulting displacement / distance on the plane when it lands?

If you just need the in-plane distance, I would compute a homography between image points and world points in the plane (the four corners of the field if the full field is visible, or some other points with known locations). If you can do that, it’s a simple matter applying the homography to the image points to get the location on the field.

If you are trying to track the ball through the full trajectory and get the path length, things get more complicated as you will need to calibrate the extrinsics for both cameras (or similar) and calculate the path length from the 3D positions. This would require synchronized cameras (so the images are taken at the same time / position of the ball) etc. A much bigger undertaking.

If it’s path length you need, I’d probably see how far I could get by using the start/end point of the ball (in field coordinates) along with the time of flight of the ball. The 3D path would be approximately parabolic, so you should be able to get a pretty good estimate that way.