What a Budget Launch Monitor Measures and What It Quietly Estimates

Buy a sub-£500 launch monitor and you get a screen with twenty numbers on it. Three of them are real. The rest are the output of a physics model that took those three real numbers, made some assumptions about your ball, the air and your club, and produced something that looks exactly as authoritative as the measured ones. Same font, same decimal places, no asterisk.

That gap is the single most useful thing a club golfer can learn about their own kit. Not because budget units are bad (they are genuinely remarkable for the money), but because the numbers you practise to should be the ones the device actually sees. Chase a modelled number and you will spend a winter fixing a fault that only exists inside a regression equation.

The three things a cheap radar genuinely sees

Doppler units like the Garmin Approach R10 (around £400 to £470), the FlightScope Mevo (about £450) and the Voice Caddie SC4 sit behind you and bounce 24GHz radar off two moving objects: the club head just before impact, and the ball just after it. From the frequency shift they get speed. From the return over the first few feet of flight they get the launch vector.

So the honest list is short:

• Ball speed. Measured. Trust it.
• Club head speed. Measured, though less cleanly than ball speed, because the club head is a smaller, less reflective target moving in an arc.
• Launch angle and launch direction. Measured, over a short window of flight.

Everything else on the screen is downstream. Smash factor is ball speed divided by club speed, which means it carries both measurement errors at once. Carry distance is a trajectory solver fed your launch conditions plus an assumed ball, an assumed temperature and an assumed altitude. Apex height, descent angle, total distance, spin axis: all model.

Spin is the interesting one, and it is where the marketing gets slippery. FlightScope is refreshingly upfront: the Mevo will not measure spin unless you stick metallic dots on the ball, one per shot, and it says so in the manual. Rapsodo’s MLM2 Pro measures real spin only with their RPT balls, which carry a printed pattern the cameras can track. Garmin publishes a table splitting the R10’s metrics into measured and calculated, and plenty of what golfers quote in forum posts sits in the calculated column.

Without a sticker or a marked ball, your spin number is a lookup. The device knows you hit a 7-iron at 105 mph ball speed with 19 degrees of launch, and it returns roughly what a population of golfers produces from those conditions. It cannot tell that you caught this one thin off a wet lie with a two-year-old Srixon.

Where the invented numbers come from

Here is a real R10 CSV export row, trimmed to the columns people actually stare at:

Club,ClubSpeed,AttackAngle,ClubPath,ClubFace,FaceToPath,BallSpeed,
SmashFactor,LaunchAngle,LaunchDirection,Backspin,SpinAxis,Apex,Carry,Total
7 Iron,78.4,-2.1,1.3,0.4,-0.9,105.2,1.34,19.1,1.8,6210,-3.2,27.4,148.6,156.9

measured:  ClubSpeed  BallSpeed  LaunchAngle  LaunchDirection
derived:   SmashFactor  FaceToPath  SpinAxis
modelled:  AttackAngle  ClubPath  ClubFace  Backspin  Apex  Carry  Total

Look at that bottom row. Attack angle, club path and face angle are the three metrics club golfers most want, and on a radar unit sitting eight feet behind the ball they are inferred from where the ball started and how it curved, not seen. The physics runs backwards: ball start line is roughly 85% face angle for a driver and nearer 75% for a mid-iron, curvature comes from face-to-path, so the device solves for a face and path that would have produced the flight it saw. Reasonable maths. Still a reconstruction, and a reconstruction that assumes a centred strike, because a toe hit gears the ball left and the model reads that as a closed face.

Strike location is the ghost in every budget unit. It is unmeasured, it shifts spin, launch and gear effect, and the model cannot see it.

Two worked examples that cost you real yards

Say you are a 12 handicapper with 95 mph of driver speed and 138 mph of ball speed, launching at 14 degrees. Your R10 says carry 220 yards and spin 2,600 rpm. You feel good. On course, that drive carries 205.

What happened: your actual spin was nearer 3,600 rpm, because you deliver the club with a negative attack angle and you play a soft three-piece ball in 11 degrees of Yorkshire air. A thousand rpm at that speed is worth somewhere around 15 yards of carry. The device never measured the spin, so the carry number inherited the error wholesale, and you spent six weeks trying to add distance you never had.

Second one, smaller and nastier. Ball speed sensitivity for a driver runs about 1.7 yards of carry per mph. If your unit reads club speed 2 mph high on a 95 mph swing (entirely plausible at the edge of the radar’s view, or with a shiny driver crown), your smash factor drops from 1.45 to 1.42. You now believe you are catching it out of the heel. You are not. You have a measurement artefact, and you are about to rebuild a perfectly good setup around it. If you want the full breakdown of which figures actually drive ball flight, the pillar on launch monitor numbers and what they mean covers the causal chain properly.

What the phone video can and cannot rescue

This is where golfers reach for an app, reasoning that if the monitor is guessing at club path, a camera will settle it. Partly true, with a hard limit.

Do the frame maths. A club head moving at 90 mph covers about 1,580 inches per second. At 60fps, standard iPhone video, that is 26 inches of travel between frames, so the shaft is a smear and impact falls between exposures. Switch to 240fps slo-mo and you get 6.6 inches per frame, which is better but still means you will almost never capture the actual moment of impact, and face angle at impact from a down-the-line phone is not a readable quantity. Anyone selling you a face angle off 60fps footage is selling you an interpolation.

What video-based AI does well is body motion, which is slow by comparison. Sportsbox 3D Golf builds a markerless 3D model from a single phone camera and returns pelvis sway, thorax bend, hand path depth, sequencing. Those are genuine measurements of things moving at 5 to 15 mph, and they are the numbers the launch monitor cannot touch. Onform and V1 Golf give you frame-accurate drawing tools and auto-trace rather than invented kinematics, which is an honest trade. Use them for positions and sequence; do not ask any of them for an impact-condition number.

Set the two tools against each other properly and each covers the other’s blind spot. Radar gives you ball speed and launch. Video gives you body motion. Neither gives you strike location or true spin, so get those from a face impact spray or foot powder, which costs £4 and never estimates anything.

What to actually practise

Track ball speed consistency, not smash factor. Hit ten 7-irons and write down the standard deviation of ball speed. Under 2 mph across ten shots means you are finding the middle; 5 mph means you are not, and no amount of path work will fix a strike problem. This works because ball speed is measured, so the dispersion is real rather than inherited from a model.

Use launch angle as your low-point feedback. If your 7-iron launches at 22 degrees when it should be nearer 17, you are adding loft through impact, and that is a genuine, measured signal you can work on with video the same afternoon.

Stickers or marked balls go on for one session a month, not every session. Ten drivers and ten 7-irons with the metallic dots on gives you a true spin baseline. Write it down. For the next four weeks, treat the unmarked spin readings as decoration and compare everything back to that baseline.

Ignore carry distance indoors entirely. The number is a model output of a model input, running two assumptions deep, and it will flatter you by 10 to 20 yards with a driver. Calibrate outdoors against a rangefinder on a still day, build your own gapping table from that, and let the screen say whatever it likes.

Next time you set up behind the ball, decide before you swing which two numbers you are watching. Everything else on that display is a conversation the device is having with itself.