How it works
A camera, a card, and physics
No radar, no stickers on your ball, nothing to buy. SmartYardage measures what an iPhone camera can honestly measure, models what physics can honestly model, and refuses to show anything else.
Your first bucket
- 1
Run the ten-second camera test (once)
Older phones and some browsers can't deliver the 60 frames per second we need. The camera test measures your real frame rate and gives you a straight pass or fail before you ever carry a bucket to the tee line.
- 2
Prop your phone against your bag
About six feet from the ball, facing across your target line, in landscape. It needs to stay perfectly still while you swing; a golf bag, a bench, or a range divider all work. Handheld doesn't, and the app will tell you if the phone moved.
- 3
Tilt until the horizon sits in the lower third
This one instruction does most of the work. With bright sky filling the frame, the camera picks a fast shutter, so the ball is a crisp dot instead of a smear, and a white ball against blue sky is the easiest thing in the world to track.
- 4
Drop a card next to the ball
Any credit-card-size card: license, hotel key, coffee card. The ID-1 standard makes every one exactly 85.6 × 54.0 mm, so its four corners tell us precisely how big a pixel is at the ball, and whether the phone is viewing at an angle. That's the entire calibration. No printouts, no measuring tape.
- 5
Wait for the green light
Before your first swing, the app checks its own homework: sky in frame, card found, ball found, 60 fps confirmed, motion blur acceptable. If your setup would produce garbage numbers, you find out now, not twenty shots in.
- 6
Pick a club and swing
The crack of impact triggers each measurement; practice swings are ignored. Shot by shot, your per-club averages build. Everything is saved on your phone, so it works with no signal, and your buckets are there next time.
What happens in the half-second after impact
At 60 frames per second, a ball leaving at 130 mph appears in roughly five frames before it exits the camera's view. In each one we find the ball, correct for the lens's wide-angle distortion, and use the card's known geometry to convert its position from pixels to real-world feet.
Five positions with precise timestamps give us the two things a camera can honestly measure: ball speed and launch angle. Spin can't be seen at 60 fps, so it's estimated from your club and launch, the way every budget launch monitor quietly does (we just say so out loud). Speed, launch, and estimated spin then go into a ball-flight model, the same drag-and-lift physics used to simulate real ball flight, which integrates the trajectory and returns your carry distance.
Every shot also gets a confidence score. Too few clean frames, a ball we lost against the trees, a card reading that disagrees with the ball's known size: any of these and the shot is marked “missed” instead of getting a number. A visible miss you can trust beats a plausible number you can't.
Accuracy, stated plainly
| Metric | What to expect |
|---|---|
| Ball speed | ±2–4% |
| Launch angle | ±1–2° |
| Carry, mid-iron | ±8–12 yards |
| Carry, driver | ±12–20 yards |
| Club-to-club gaps | Much tighter. Errors are systematic within a session, so they mostly cancel in the gaps |
If you need ±1 yard, you need a four-figure radar unit and we'll cheerfully tell you so. If you want to know your real gaps and whether that swing change added five yards, that's exactly what this measures well. Every constant and coefficient in the flight model traces to a published reference. See the full list of sources.
What you need
- A modern iPhone: the beta is tuned on iPhone 11 Pro Max and newer. The camera test gives your phone a definitive yes or no.
- Safari: SmartYardage is a web app. Add it to your home screen when prompted; that's what keeps your shot history safe long-term.
- Outdoors, in daylight: the measurement needs sky in the frame and real light. Indoor and covered bays aren't supported yet, and we'd rather say that than hand you bad numbers.
- Any credit-card-size card: you already have five.
Start with the ten-second test
It measures your phone's real frame rate and tells you honestly whether the measurement path will work on your device.
Test your iPhone