30th of July 1966. Wembley Stadium, London. World Cup Soccer finals. England 2, Germany 1. For the English team victory was tantalizingly within reach. Victory was just seconds away. Victory looked inevitable.

And then the unthinkable happened.

In the 89th minute of the game, Lothar Emmerich of Germany took a free kick that hit the wall of defending English players. On rebound, German center-forward Siegfried Held kicked the ball into the body of Karl-Heinz Schnellinger. The deflected ball was picked by German striker Wolfgang Weber who scored the stunning equalizer! Germany had miraculously averted defeat.

The match went into extra time. It was destined for intense drama. In the next few minutes history would be written with bitterness that would last a generation.

The Wembley Goal

11 minutes into extra time, Geoff Hurst kicked a swivel shot towards the German goal, and world watched the ball as he fell to the ground. The ball hit the underside of the crossbar, and droped vertically. According to the rules of soccer it is a goal when “the whole of the ball passes over the goal line.” Millions of TV viewers waited in intense anticipation as the referee Gottfried Dienst consulted the linesman Tofiq Bahramov from Azerbaijan. Tofiq indicated it was a goal. Crowd at Wembley erupted in celebration!

A crest fallen German team went on to lose the game 4-2 when Geoff Hurst scored his third goal of the game — a hat-trick! To this day Tofiq Bahramov is referred to as the the “Russian linesman” in Germany, and rumors (most probably false) circulated that in response to being asked why he declared a goal, he replied with a single word — “Stalingrad”.

This goal is referred to as the “Wembley Tor” or “Wembley Goal” in Germany. For decades the controversy lingered on . In England people generally believed it was a goal, and in Germany people generally felt cheated out of a World Cup victory.

This is how the English fans remember the goal.

And this is the how the German fans remember the goal.

It is literally a difference in perspective!

The Computer Vision Solution

The ball did not cross the goal line by at least 6 centimeters

I met Dr. Andrew Zisserman, co-author of the most authoritative book on Multiple View Geometry, at a Computer Vision conference in 2004. When I got a chance, I shook his hand and said, “World Cup Soccer Finals, 1966.” He gave a wide smile. His face lit up. I ended up talking to him for the next 10 minutes about his paper, Goal-directed Video Metrology with Dr. Ian Reid that conclusively proved that Wembley Goal was in fact not a goal! The ball did not cross the goal line by at least 6 centimeters taking into account various sources of measurement errors. When the most diehard English fans heard about his paper and the conclusion, they accused Dr.Zisserman, a top English researcher, of being a German spy!

Video footage of the game was available from two different angles, but it is still a very hard problem to solve. They mention the following challenges in the paper

The internal calibration of the cameras is unknown and may vary during the sequence. The motion of the cameras was unknown and so was the relative motion between the two cameras. For many frames, there were very few features available off the ground plane. The frames from two different cameras were not synchronized.

However, think a bit harder and you see there is more information in the video sequence.

The ground is close to a plane and visible in both cameras. Images of a plane seen from two different cameras are related by a transformation called a Homography. The goal post bars are close to vertical to the ground plane and are visible in both cameras. The motion blur in the most important pair of frames was negligible.

Given the above information, they proved in the paper that the projection of the ball onto the ground plane ( i.e. the location where the ball landed on the ground ) could be uniquely calculated. After accounting for synchronization error and radial distortion of the lens, they concluded that the ball did not cross the goal line by at least 6 cms.

Another study by Dr. Duncan Gillies of Imperial College London apparently came to the same conclusion, but I could not find the original paper.

One would think that these papers would put an end to the controversy. Did they ? Hell no, soccer is a religion. In a 2013 Sir Geoff Hurst welcomed goal line technology saying, “If we had this system 50 years ago, it would have shown quite clearly the ball was at least a foot over the line.” Now that is quite an irony — welcoming technology and ignoring it in the same sentence.

Revenge or Injustice ?

In a 2010 World Cup game England was playing against Germany. English player Frank Lampard’s shot hit the crossbar, and comfortably crossed the goal line by about a foot. He was denied a goal! Germany won 4-1. Some call it a revenge for Wembley. I call it injustice. The uproar that followed forced the luddites at FIFA to approve the use of goal line technology in 2012.

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