GPS devices and laser rangefinders both tell you how far you are from the target, but they measure distance in completely different ways. Here is how each works, where each is accurate, and what the Rules allow.
Knowing the exact distance to the green is one of the simplest ways to make better club choices. Two technologies dominate: GPS devices, including phone apps, watches and handheld units, and laser rangefinders. Both answer the question "how far?", but they work in fundamentally different ways, and that affects when each is most useful.
How GPS golf devices work
A GPS device calculates your own position using signals from navigation satellites. On its own, that tells it where you are, not where the green is. The second ingredient is course mapping data: a digital map of each hole with the positions of tees, greens, bunkers, water hazards and other features.
The device compares your position with the mapped points and calculates distances, typically to the front, middle and back of the green, and to the carry and edge of hazards.
Strengths
- Distances to features you cannot see, such as a green behind a hill or the far side of a bunker
- Instant front, middle and back numbers without aiming
- Hole overviews and, in many apps, shot tracking and statistics
Limitations
- Accuracy depends on both the satellite fix and the quality of the course map. Consumer GPS is typically accurate to within a few metres in good conditions; a poorly mapped course adds error.
- Most devices do not know where the flag is today, unless the app lets you place it manually.
- Course changes, such as a rebuilt green, can make old map data wrong; see how golf course mapping works.
How laser rangefinders work
A laser rangefinder sends out pulses of invisible laser light and measures how long they take to reflect back from the target. Because light travels at a known speed, the time gives the distance. Golf rangefinders use target-priority modes so they lock on to the flagstick rather than trees behind it, often confirmed by a vibration.
Strengths
- Exact distance to the flag, wherever it is positioned today
- Distance to any visible object: a tree, a bunker lip, a fairway marker
- No dependence on course maps or phone signal
Limitations
- You need a line of sight to the target
- Steady hands help; aiming at a distant flag takes practice
- No information about hidden hazards or the shape of the green
Slope and "plays like" distances
Many devices offer a slope function that adjusts the distance for elevation change: an uphill shot plays longer, a downhill shot shorter. Some also factor in temperature or altitude. These features can be helpful in practice and casual rounds.
What do the Rules allow?
Under the Rules of Golf published by The R&A and the USGA, players may use devices to obtain distance information unless the committee running the competition has adopted a Local Rule prohibiting them. However, using features that measure elevation changes or give club or swing advice during a round is not allowed. Many devices include a tournament mode that switches off slope. Always check the terms of any competition you enter; the official Rules of Golf explain the details.
Which should you choose?
| If you mostly want... | Choose |
|---|---|
| Exact distance to the flag | Laser rangefinder |
| Front, middle, back and hazard distances at a glance | GPS watch or app |
| Help on unfamiliar courses with blind shots | GPS |
| Shot tracking and statistics | GPS app or watch |
| Both | A hybrid device, or a rangefinder plus a phone app |
Distances only help if you know how far you hit each club. A practice session with a launch monitor answers that; see launch monitor numbers explained.
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