Why Semi-Automated Offside Produces A Timestamp, Not A Picture

The three-dimensional offside graphic shown after a review is not evidence. It is a rendering produced from the system's numerical output for the benefit of viewers.

The system solves two problems

Offside requires knowing the moment the ball was played and the positions of the relevant players at that instant. Both were previously judged by eye at speed.

Automation addresses each separately. Sensors and tracking identify the moment of contact, and limb tracking establishes player positions at that timestamp.

The output is a set of coordinates and a time, which the system compares to determine whether a player was beyond the second-last defender.

Why the moment is the harder half

Player positions are tracked continuously and are relatively easy to interrogate at any instant. Identifying the exact frame of contact with the ball is less straightforward.

At normal frame rates, contact can fall between frames, and the difference of a single frame can change the outcome on a marginal call.

Ball sensors that detect the moment of a kick directly were introduced to address this, replacing a visual judgment with a measurement.

What the graphic actually shows

The rendered image places virtual lines through tracked limb positions at the determined timestamp. Every element is drawn from data rather than photographed.

This is why the graphic never disagrees with the decision. It is generated by the same system that made it, and it cannot show anything else.

Broadcasters present it as visual proof because it reads that way to an audience. It is closer to a diagram of a calculation.

Precision is not the same as certainty

Tracking systems have measurement tolerances, and a decision resting on a margin narrower than that tolerance is not really determined by the data.

Competitions have addressed this partly with tolerance rules and partly by not disclosing margins, since publishing a figure inside the error band invites argument.

The debate about whether offside should have a tolerance is therefore a debate about how to represent measurement uncertainty in a binary rule.

The speed gain is the actual change

The system's main effect is time. A decision that took a video official a minute to construct manually is produced in seconds.

Accuracy improved less than speed did, because the manual process was already accurate when given enough time. The bottleneck was the drawing of lines by hand.

What changed for the record is that offside determinations are now logged as data rather than as a human conclusion, which makes them reviewable in a way they were not.

The phrase you hear in selection meetings is that a player is one-dimensional. It is said as a criticism. I have never fully understood why, given that the format is short enough that a team only needs a handful of dimensions in total and can distribute them across eleven bodies.

Consider the batter who can only hit down the ground and only against pace. He is useless in the middle overs against two spinners on a turning surface. He is also, in the right six deliveries, the most valuable player on the field, because the thing he does badly never comes up and the thing he does well comes up repeatedly.

The counter is obvious and it is about flexibility. If a wicket falls at the wrong moment, a specialist walks into a situation he cannot handle, and you have burned a slot. That is real. But it is a scheduling problem, not a talent problem, and scheduling problems have solutions that talent problems do not.

What actually happens is worse than either. Sides pick a squad full of players who are competent in every phase and outstanding in none, then wonder why they keep posting adequate totals and losing to somebody who had one man go berserk for four overs. Competence across the board is a way of guaranteeing you are never the reason a match turns.

I would rather carry two narrow players and accept that in a third of matches one of them is dead weight. The distribution of outcomes matters more than the average, because you do not get half a trophy for finishing consistently mid-table in a knockout competition.

There is a coaching dimension to this that gets ignored. Telling a specialist to broaden his game usually makes him worse at the thing he was picked for, because the technique that lets a player hit a length ball over long-on is not the technique that lets him work it into the leg side. They fight each other. He ends up in the middle, hitting neither shot with conviction, and within a season he is a squad player.

Leave him alone. Let him be strange.

The best selections I have watched were not the most complete cricketers on the list. They were the ones whose weakness the captain had a plan to hide.