How do golf launch monitors work?

Doppler radar units

Radar launch monitors send out microwave signals and measure the reflections. When the club and ball move, the reflected signal changes frequency, the Doppler effect, and the unit uses that change to calculate speed. By tracking the ball over time, larger radar systems can follow its flight. Personal radar units such as the Voice Caddie SC4 Pro, SC300i and the PRGR monitor sit behind or beside the ball and are listed as using Doppler radar.

Radar is good at speeds: club speed and ball speed are its strength. Outdoors, with a long ball flight to track, it can follow the ball and derive launch and spin. Indoors with a short flight into a net, small radar units have less flight to work with, so makers give minimum distances to the net.

Camera units

Camera-based launch monitors take rapid images of the ball in the moments after impact. From the change in position between images they measure ball speed, launch angle and direction. By reading the rotation of markings or texture on the ball, they can measure spin rate and spin axis. Some also photograph the clubhead to measure club data. Because everything happens within a short distance of the ball, cameras suit indoor use with a net close by.

The trade-offs are lighting, which needs to be bright and even, and the requirement for a clear view of the ball. Larger studio units built into simulator bays usually rely on cameras for this reason, and some personal units mount beside the ball rather than behind it so the cameras can see impact clearly.

Hybrid units

Several personal units combine both methods. The Rapsodo MLM2PRO listing describes dual optical cameras plus radar processing, with 6 of its 13 metrics measured, including spin rate and spin axis. The SkyTrak ST MAX listing describes dual Doppler radar plus photometric cameras. Combining methods lets each handle what it does best: radar for speeds, cameras for launch and spin.

Compare launch monitors by technology →

Measured versus calculated numbers

No personal launch monitor measures everything. Simple units measure club speed and ball speed and then estimate carry from those, using typical launch and spin values. Better units measure launch angle and spin too, which makes carry estimates more realistic. Carry, total distance, apex and curve are almost always calculated from the measured inputs using a ball flight model.

This is why two units can show different carry numbers for the same shot. If a listing says some metrics are measured and others derived, as Rapsodo's does, take the measured figures as the most reliable. Our numbers explainer covers what each figure means.

What this means when buying

Our under £700 guide compares lower priced units on these points.

• Want speed training only: a simple radar unit such as the PRGR or Swing Caddie SC200 Plus is enough.
• Want to understand ball flight: choose a unit that lists launch angle and spin.
• Practise mainly indoors: favour cameras or hybrids that state indoor use.
• Practise mainly on an open range: radar units work well.

Note:Radar and camera units are low power consumer devices, but always follow the maker's set-up guidance, keep the unit out of the line of the ball and allow safe space to swing indoors.

Frequently asked questions

Are radar or camera launch monitors more accurate? Each is better at different things. Radar excels at speed and long flight; cameras excel at launch and spin near the ball. Hybrids aim to combine both.

Why does my launch monitor show a different carry from the range? Carry is usually calculated from measured speed, launch and spin. Different ball flight models, range balls and conditions all cause differences.

Do I need spin data? If you want to understand curve and height, yes. For speed training, it is not essential.