Radar and Camera Units Are Not the Same Instrument
Every launch monitor reports a long list of numbers. Only some of those numbers are measured. The rest are calculated, and which is which depends entirely on the technology.
A golfer standing in a bay sees a screen with twenty figures on it and reasonably assumes the machine measured twenty things. It did not. Every launch monitor measures a handful of quantities directly and derives everything else from a model. The useful skill is knowing which column you are looking at.
Doppler Radar: Watches the Ball
A radar unit sits behind you and emits a microwave signal. The ball flying away shifts the frequency of the returning signal, and from that shift the unit derives speed and, tracked over time, the shape of the flight. Better radar units also pick up returns from the clubhead just before and after impact.
What radar measures directly and well:
- Ball speed
- Launch angle
- Spin rate, when it gets a clean return
- Actual carry and total distance, because it watched the ball travel
- Flight curvature, because it tracked the whole arc
What radar derives rather than measures: most club-delivery numbers. Face angle, club path, and attack angle come from a much weaker set of returns off a small, fast-moving clubhead. Modern units are good at this and getting better, but it is inference from a difficult signal rather than direct observation.
Radar's other constraint is space. It needs the ball to fly a meaningful distance to work well — commonly six to eight yards minimum, and considerably more for reliable spin. A radar unit in a small indoor bay is working with a fraction of the data it was designed to collect.
Photometric Cameras: Watch the Impact
A camera-based unit sits beside or above the hitting area and fires high-speed exposures in the milliseconds around impact, then compares images to extract positions and rotations. Many units mark the ball or use its dimple pattern to read spin axis directly.
What cameras measure directly and well:
- Clubhead speed, face angle, club path, attack angle, and dynamic loft
- Impact location on the face
- Spin rate and spin axis, read from the ball itself rather than inferred
- Ball speed and launch conditions in the first few inches
What cameras derive rather than measure: everything after the ball leaves the frame. Carry distance, total distance, peak height, and curve are outputs of a flight model fed by the measured launch conditions. The model is good. It is still a model, and it is applying assumptions about air density and spin decay that may not match the day.
| Quantity | Radar | Camera |
|---|---|---|
| Ball speed | Measured | Measured |
| Launch angle | Measured | Measured |
| Spin rate | Measured, needs distance | Measured at impact |
| Club path / face angle | Derived from weak returns | Measured |
| Impact location | Not available | Measured |
| Carry distance | Measured outdoors | Modelled |
| Peak height | Measured outdoors | Modelled |
The Practical Consequence
Read the table one more time and the fitting implication falls out of it. If the question is about what the club is doing to the ball — strike location, face-to-path relationship, dynamic loft — a camera unit is the right instrument, and it works perfectly well in a confined space.
If the question is where the ball actually goes on this particular day, a radar unit outdoors is the right instrument, because it watched the ball do it rather than predicting it.
Why Two Units Disagree
Golfers regularly tell us their carry number at one facility differs from another by fifteen yards. Usually nothing is broken. Consider what has to line up for two readings to agree:
- The same ball. A range ball and a premium urethane ball differ by more than most people believe.
- The same environment assumption. A camera unit set to sea-level standard conditions is not going to match a radar unit measuring in ninety-degree humid air.
- The same definition. Some units report carry to first bounce, others to a modelled landing point on flat ground.
- The same normalisation setting. Many units offer a "standard conditions" mode that silently adjusts output.
Once you account for those four, most disagreements shrink to a couple of yards.
What We Run
Camera units in the bays and a radar unit on the tripod outside, which is why our sessions are structured the way they are. The bay tells us what your club is doing and lets us compare candidates fairly. The radar unit outside tells us where the ball lands in today's air.
When those two disagree about which shaft won, we go with the one that was measured rather than modelled.
Come Look at Both Screens
Every session uses both instruments, and the spec sheet notes which number came from which.