Judging the measurement

Last month I went to watch the Grand Final. And a Grand Final it was too: a non-stop contest throughout the 80 minutes, without any of the time wasting, play acting and whingeing that we have to tolerate in what is laughingly called 'the beautiful game'. Neither was there a managerial rant after the game despite the fact that the game was heavily influenced by a video referee decision. After many years of being a bad loser and exhibiting the footballers’ trait (probably the only footballers' trait I excelled at) of moaning at referees and their decisions (even when just a neutral spectator), I am gradually developing the mature rugby attitude of accepting the decisions as they are made. My moaning has not gone away but I now direct it at the commentators and their inane comments.

Yes, you have guessed it, there is a however! It is to do with the video referee's decision. I didn't agree with it but that doesn't matter. What does matter is that it was based on flawed measurement. As an NDT engineer, I see myself and my colleagues as measurement professionals and therefore feel justified to pass comment. The situation also holds lessons relevant to NDT. If you look at the comments posted on the internet after the match you will see that as many people agreed with the referee's decision as disagreed with it. It is well known that different people will see different things when looking at the same object. We have seen it happen regularly in NDT. When people have a desire for a particular outcome then they will be predisposed to interpret the information in favour of that outcome. The video referee is a professional and so the starting point is that he is impartial and had no predisposition and was looking at the images objectively to establish his decision.

At the risk of being accused of protesting too much, I have no complaint with the decision. What I do have a gripe with is the explanation which was subsequently given: although the winger's body was in front of the kicker, his one foot that was on the ground was behind the kicker. So the referee has measured the position of one player’s foot relative to another player's foot, who happens to be a number of metres away, to an accuracy of some centimetres by looking at videos, without any digital processing or measurement aids, obtained from elevated, mobile cameras which are placed many more metres away and subtend unknown and different angles to the players. He may have been able to form a view of whether the player was offside but his 'measurement' would have had large error bars which, as they sometimes are in industry, were conveniently ignored.

The disguising of a judgement by implying a precision of measurement was also evident in the recent Manchester football derby. The explanation for the time beyond the 90 was based on four minutes of added time, 56 seconds between the ball crossing the goal line and play restarting, 30 seconds for a substitution. So the time that should have been added was five minutes, 26 seconds. The goal was scored at five minutes, 27 seconds and the full-time whistle was at 96 minutes and 58 seconds. From this explanation you would be forgiven for believing that the referees controlled the game to the nearest second, even though substitutions are rounded to 30 seconds. Prozone figures show that, in elite football matches, the ball is out of play on average between 35-55% of the time. This equates to approximately 30 to 50 minutes of the 90. So added on time is always going to be an approximate judgement and to indicate otherwise is wrong, unless there is a written methodology which lays out exactly how it should be calculated.

Measurement and judgement are inexorably linked. The greater the errors in the measurement; the greater the requirement for subjective judgement. Referees and engineers live in a world where decisions have to be made based on the available evidence. For those decisions to be made effectively, and for the decisions to be understood by others, there are two requirements: competence of the person making the measurement that informs the judgement; honesty about capability of and the errors inherent in the measurement. The certification of the competence of operators has always been, and continues to be, a subject of scrutiny in the NDT profession, and maybe there is a business opportunity to provide support to video referees in analysing the images. However, I believe that there is still room for improvement in honesty regarding capability and errors – even if the client doesn't want to hear it!

Please note that the views expressed in this column are the author's own personal ramblings for the purpose of encouraging discussion within the NDT Newspaper. They do not represent the views of the IVC, Serco Assurance or the HSE who funded the PANI projects.

Letters can be mailed to The Editor, NDT News, Newton Building, St George's Avenue, Northampton NN2 6JB. Fax: 01604 89 3861; Email: ndtnews@bindt.org or email Bernard McGrath direct at Bernard.McGrath@sercoassurance.com