What the Quarterly Lane Check Actually Catches

In the calibration world there is a distinction between calibration and verification that golf never adopted and probably should. Calibration means adjusting an instrument so it agrees with a reference. Verification means checking whether it still does, documenting the result, and doing nothing else.

What we do quarterly is verification. Nobody touches a setting. Two people hit five clubs indoors and then outdoors on the same morning, and the numbers go in a log whether they are convenient or not. If a drift appears, the investigation starts afterwards.

The Morning, Step by Step

It runs from about seven until noon and it is deeply tedious, which is a feature.

• The five reference clubs come off the rack and go on the bench: loft, lie, length, swing weight and butt frequency, all recorded before anything is hit.
• Both bay instruments get a station check: position, height, distance to the ball, level, and firmware version noted.
• Air data is taken in the bay and again at the lane, at the start of every block rather than once for the day.
• Blocks of eight strikes alternate between bay and lane, with the two staff running the order in opposite directions.
• Outdoors, pitch marks are spotted and measured. Not resting places.
• Everything goes into the log unfiltered, including the mornings where somebody was hitting it badly.

What Has Drifted

Three things, in ten years. All three were caught by this check and none of them would have been obvious from inside a normal working week.

A firmware update changed a spin algorithm. In 2019 the doppler unit received an update that improved spin reporting for low-speed shots. It also shifted mid-iron spin readings by about ninety revolutions relative to the previous version. Nothing was broken and the change was almost certainly an improvement, but every card written before that date and every card written after it were now on slightly different scales. We noted the version boundary in the log and have printed firmware versions on cards ever since.

The mat wore in. Bay 4's hitting surface reached a point around its fourth year where the base under the strike zone had compacted. The offset for irons drifted by about two yards across three consecutive checks before anyone would have noticed it from the inside. The mat was replaced and the offset moved back. We now replace on a schedule rather than on appearance.

A reference club stopped being a reference. The seven iron we had used since 2015 measured half a degree weak in 2022. Half a degree is entirely normal for a forged head hit several thousand times, and it is also enough to corrupt a table that assumes the club has not changed. It was bent back, the event was logged, and we now measure the reference clubs at every check rather than annually.

What Has Never Moved

Worth saying, because verification records tend to get quoted only when they catch something.

The units themselves are good. That is the honest summary of ten years of records. The things that drift are the surroundings: the mat, the reference clubs, the software version, and the weather. An instrument accuracy specification is a claim about the box on the tripod and says nothing about any of those.

Ten years of checks have never once found the instruments to be the problem. They have found the mat, the clubs, and a software release.

Why the Doors Are Shut on Mondays

The quarterly lane check is the big one. The weekly version happens every Monday and is smaller: station positions, a short reference set in both bays, the bench fixture against gauge blocks, and the scales against a certified mass.

Closing a day a week to customers is expensive and it is the reason the units have never quietly drifted between quarterly verifications. A studio that checks its equipment only when something looks wrong will find out about a drift from the drift's consequences, which by then are sitting on somebody's cards.

The Log Is Not Private

The verification log lives in a binder at the desk and anyone can read it. It contains mornings where the numbers were poor, the 2019 firmware boundary, the mat replacement, and a page from 2021 where an entire session was voided because the lane had been mown to a different height that week and nobody checked first.

That last one is the most useful page in the binder. It is the clearest reminder that a verification procedure with an unexamined assumption in it produces confident, wrong results, and that the assumption is usually something nobody thought was a variable.

Corrections: none since publication. The next check falls in the second week of March; the resulting table is issued within ten days of the morning.