If you want to measure your shots today, you usually buy a radar unit: hardware from about 600 dollars, often plus a subscription for courses and features. We asked ourselves whether it could be done without. A current iPhone has a camera that films 240 frames per second and a chip that runs neural networks in milliseconds. That should be enough.
It is. The DeepSwing launch monitor measures every real ball on iPhone and Android. Here is how the measurement chain works, how accurate it is and where its limits are.
1. The camera: short exposure beats high resolution
A golf ball leaves the club at well over 200 km/h. With normal exposure it becomes a smeared streak in the video. That's why we film at 240 frames per second with an exposure time of 1/8000 of a second. The ball stays a sharp dot in every frame, as in the cover image above.
The price: it needs light. Outdoors in daylight that's no issue; in a hitting bay or a basement, bright and even lighting is part of the setup. Avoid hard shadows right above the ball.
2. Arming instead of always computing
Detection knows three states. Searching: where is the ball? Armed: the ball rests in the marked zone, now we wait for the strike. In the app the circle turns green and the status reads "Ready, hit it!". Impact: the ball is moving, now every frame counts.
Full-precision computation happens only around the strike. That saves battery and prevents false triggers when someone just walks across the mat. The app finds the next ball on its own.
3. Two models: club head and ball
For the club head we trained our own detection model on a current YOLO architecture and optimised it as a Core ML model for the Neural Engine. It finds the club head in the frames just before impact and measures its speed. How the model was built is described on our club head detection page.
For the ball, a few frames after impact are enough: the displacement from frame to frame gives ball speed, vertical launch angle and start direction. Club head and ball together give the smash factor: how efficiently the ball was struck. What each number means is covered in Launch monitor numbers explained.
4. Physics: from launch to landing
The measured launch values feed a ball flight model that accounts for drag, lift, wind and air density. From it come carry, total distance, apex and landing angle. The app simulates bounce and roll on the 3D range. On real courses the ball then flies over terrain built from laser-scan elevation data.
What is measured, computed and estimated
We care about being honest about the measurement chain, so here is the split:
| Number | Where it comes from |
|---|---|
| Ball speed | measured, from the frames after impact |
| Launch angle and start direction | measured |
| Club head speed | measured, from the frames before impact |
| Smash factor | computed: ball speed divided by club speed |
| Carry, apex, landing angle | computed with the ball flight model |
| Total distance | simulated, with bounce and roll |
| Spin | estimated from club, speed and launch |
How accurate is it?
We measured DeepSwing against a radar launch monitor, the Rapsodo MLM2 PRO. Depending on the club, our carry is within 0 to 2 percent. At 150 metres that is three metres in the worst case.
There is one limitation we state openly: we don't measure spin directly. That would require seeing the ball rotate, tracking markings on the ball in a very short time. We estimate spin and label it that way in the app.
Setup in two minutes
Most measurement errors don't come from the model but from the setup. This is how the phone stands right:
- Put the tripod opposite you, on the other side of the ball, about 1.5 metres from it, so your follow-through can't reach it.
- Mount the phone in landscape, 1 to 1.5 metres high and tilted slightly down, so the ball sits in the marked zone.
- Align it: lay a club on the ground pointing at your target and turn the tripod until the yellow line runs along the club. The app tells you once the phone is less than 1.5 degrees off level.
- One ball in the zone only, and don't touch the tripod afterwards.
If the tripod stands at an angle to the target line, every ball starts far to one side. The app spots the pattern and tells you.
Phone or radar?
A radar unit has advantages, depending on the model a directly measured spin, for example. For most golfers who practise into a net at home or on the range, other things matter more:
| Phone with DeepSwing | Your own radar unit | |
|---|---|---|
| Hardware | the phone and tripod you already own | a dedicated device from about 600 dollars |
| Cost | 5 free shots a week, then from €8.99 a month or €169.99 once | the device, often plus a subscription |
| Carry | within 0–2% of the MLM2 PRO | reference |
| Spin | estimated | measured on some devices |
| Display | iPad, Mac, TV, Google TV, projector, GSPro | depends on the device |
From measurement to game
Because it's all software, it doesn't stop at the number. The phone measures, the display runs on iPad, Mac or big on a projector. There is a daily challenge, mini games for up to four players, putting and more than 12,000 real courses. If you use a PC simulator, the shots go to GSPro, as described in How to connect GSPro to your phone. And if you want to set up a room of your own, Golf simulator at home with your phone has everything you need.
The principle of finding and measuring small, fast objects in high-speed video is not limited to golf. More on our ball detection page.
Frequently asked questions
Does the launch monitor work on Android?
Yes. DeepSwing is on Google Play with the same launch monitor, including the 3D range, games, putting and real courses. A tablet or Google TV becomes the big screen.
Do I need a particular iPhone?
The camera has to film 240 frames per second. A stable tripod matters more than the newest model.
Does it work indoors?
Yes, into a net in the basement, the garage or a hitting bay. What matters is enough light and a tripod that doesn't move.
How much does it cost?
Five shots a week are free. After that the launch monitor costs €8.99 a month, €89.99 a year or €169.99 once.
Try it yourself: the DeepSwing launch monitor for iPhone and Android.