The Number That Won't Hold Still

MyGolfSpy ran twelve launch monitors side by side, from a $500 box to a $5,000 unit, and asked a question most golfers never think to ask: when two devices watch the same swing, how much do they actually agree? The answer, reported in their twelve-monitor test, is that they agree on most things and quietly disagree on the one that matters most.

Ball speed held steady across the field. So did the broad strokes of carry. The metric that came apart was spin. Indoors, the cheaper units drifted 20 to 30 percent off the reference system, while the premium units clustered tight. Carry followed spin down the same crack — four to five percent of deviation outdoors, most of it traceable to small errors in launch and spin that compound by the time the ball lands. Launch angle, the metric nobody reads, showed double-digit percentage swings on some indoor units.

The cause is structural, not a defect. As MyGolfSpy lays out, every launch monitor runs on algorithms. The separation is how much each one measures directly versus how much it estimates. A camera-based unit watching the ball rotate is reading spin. A radar unit behind an impact screen, with the flight cut short, is inferring it from club delivery. Both can be useful. They are not the same number, and the gap is widest exactly where the golfer is paying closest attention.

This matters because spin is the number amateurs chase hardest with a driver, and for good reason. Spin is downstream of attack angle. Hit down on the ball and you add loft at impact and strike low on the face, and both of those send spin up and carry down. So a player reads 3,200 RPM on a sim bay screen, decides the driver is the problem, and goes looking for a fix. But which 3,200? On a camera unit that reads spin directly, that number means one thing. On a radar unit estimating behind a screen, it might mean 2,800 with a confident-looking display. The player can't see the difference. The screen doesn't tell them.

There's a second layer the test exposes. The same device gives you different answers in different settings. Indoor radar behind a screen estimates more than outdoor radar with full flight. So a golfer comparing last winter's sim numbers to this spring's range session isn't comparing two performances. They're comparing two measurement methods and calling the difference progress, or panic.

None of this is an argument against launch monitors. The data is the best feedback an amateur has ever had access to, and the worst unit in the test still beats hitting balls into a net with no numbers at all. The argument is narrower: a number without its source attached is half a fact. The reading is only as honest as your memory of where it came from, and most golfers don't keep that memory at all. They keep the number. The number drifts. The conclusions drift with it.

The cleanest version of the discipline is boring. Log the device next to the reading. Compare indoor to indoor and outdoor to outdoor. Treat a 400-RPM swing between two sessions on two different monitors as noise until proven otherwise. Trust the trend on one device over the snapshot across many. A single Trackman bay watched over six weeks tells you more than six bays watched once.

This is the kind of pattern The Cut watches for you. When you log a sim session, it records which launch monitor produced the numbers, so a SkyTrak spin reading and a Trackman spin reading don't get averaged into a number that never happened. Its club breakdown trends each metric against your own prior window rather than against a stranger's optimal chart, and its baseline layer carries the known biases of each device — which ones inflate carry, which ones under-read spin — so the coaching accounts for the instrument before it judges the swing. The point isn't to distrust your monitor. It's to remember what it is: one camera, or one radar, with a method and a margin, watching one swing at a time.

Twelve devices watched the same golfer and disagreed most about the number he cared about most. That's not a flaw in the tools. It's a reminder to read them like a scientist reads an instrument — with the source written down.

Sources: MyGolfSpy, "We Tested 12 Launch Monitors Ranging From $500 To $5,000"; MyGolfSpy, "If Your Driver Spins Too Much, This Is Why".