Hawk-Eye

Goal-line technology

http://www.youtube.com/watch?v=exEHTO-YnuE

Contents

• Introduction

• What it can do?

• What does it contain?

• How does it work?

• Applications (Tennis)

What is champion’s secret?

Start match by imagining you were 0-3 down

• Your weaknesses

• Opponent’s strengths

• Umpiring errors

Introduction

Low-cost

Real-time

Passive system

Easy installation

What can Hawk-eye do?

• Track the path of the ball

• Visualize path of the ball

• Third referee

What does Hawk-eye contain?

• Tracking System

• Camera

• Speed gun

• Video Replay System

Tracking System

What does Tracking System do?

• Speed of the ball

• Swing of the ball

• How much the ball bounced

Hawk-eye Camera

Speed gun

Video Replay System

How does it work?

Principle of Hawk-Eye Triangulation

l

d

Camera calibration

Ball identification • What are we going to use?

• Shape, size, enough?

• What about shadow?

• Position of sun and previous position

Geometric algorithm

• Simple case

• Cameras at ground

1depth=r- rcosθ+ x sinθ

Track and Predict

• 3D coordinates in time sequence

• Weirestrass’ Approximation

Application

• Cricket

• Tennis

• Snooker

• Football

• Military power

• Automobile industry

Other applications

Wheel alignment • Track the enemy location • E-2C aircraft

Tennis

2D (x,y) 3D (x,y,z) 4D (x,y,z,t) Bounce Mark

IN or OUT

http://www.youtube.com/watch?v=jlSzirlFjuc

System Block Diagram

Image Plane Ball Tracking

Camera PTZDetermination

Court line extractionImage DataExtracted

Lines

CameraPose

3D ReconstructionImpact Point

DeterminationTrack Fitting3D Tracks

Linked 3DTracks

2D Tracklet

Complete Track

Each Camera

Main processes

• Real Time Issues

• Camera calibration

• PTZ Determination

• Image Plane Ball Tracking

• 3D Reconstruction

• Impact Point Determination

Real Time Issues

Camera Calibration

3D Reconstitution

TrackingVisualization

Camera Calibration

Camera Calibration

Camera Calibration

Camera Calibration

TCP/IPTCP/IP

Camera calibration vs. PTZ

calibration

PTZ

Image observations

Model-based tracking

3D ModelCourt lines

Focal lengthAspect ratio

Optical center locationCamera location

Camera attitudeFocal length

parameters

Camera calibration

• Radial distortions

• Piecewise linear approximation with various zooms

• Full resolution static image

• Court fully filling the field of view

PTZ Determination

• Pan/tilt/zoom (PTZ) motion measured on each

frame before any subsequently extracted ball measurements

• Alpha-beta predictor is used to initiate the parameters

• Re-acquisition: binary subdivision search across the PTZ parameters

Image Plane Ball Tracking

LMR algorithm

Closed boundaries

Filtered on size and shape

Candidate balls

Coordinates

Stationary camera

Polynomial fit to

predict

Perspective projection Trajectory quality

(length and movement)Acceptable tracks

3D Reconstruction

Compound Tracks

Partial Tracks

Pairs of overlap tracklets

Triangulate3 equally spaced

points

candidate Partial Track

polynomial model

2/3

Impact Point Determination

Rule-based

Bounce

Strike

Half volley

Approximate join point

Kalman Filter

velocity directions positions

New applications

• Sports simulators

• Coaching system • Hawk-Eye ball tracking system

• Broadcast quality video

• High speed biomechanical analysis

Football Simulator

• Measure speed and accuracy of their shots

• Shots replayed and analyzed in a video

• Images taken can upload to Facebook, Twitter and YouTube

References

• http://www.hawkeyeinnovations.co.uk/

• http://www.scribd.com/doc/84631898/Hawk-Eye-Technology-Ppt

• N.Owens. Hawk-Eye tennis system

• Graham Thomas. Sports TV Applications of Computer Vision

Thanks and Questions