Setting the off-route alert for trail running
Why a watch waits 25 metres before it buzzes, when 15 or 40 is the better setting, and what an alert can and cannot tell you on a trail.
The most useful thing a watch does on a trail is also the simplest: tap your wrist the moment you are no longer on the trace. Not a map to squint at, not a voice, a tap. You glance, you see the trace a few metres to your left, you step back onto it. Ten seconds lost instead of a kilometre.
This is how that alert works in Ridge, and how to choose the one number it depends on.
What the watch actually measures
Every time the GPS gives a new position, Ridge measures the distance from that point to the nearest point of the trace. While that distance stays under the threshold, you are on the route. The moment it exceeds it, you get one haptic tap, and the watch shows how far off you are. When the distance drops back under the threshold, you get a second, different tap: back on the trail. Between the two, nothing nags you; the number on the screen is there if you want it.
On an iPhone-recorded run the same events are spoken instead (“Off route, check your map”, then “Back on the trail”), so the phone can stay in the pocket. Watch runs use the wrist only.
Why not zero metres
Because GPS is not a point, it is a cloud. In open terrain a modern watch places you within roughly 5 to 10 metres. Under dense forest, against a cliff or in a narrow gorge, the reflected signal can put you 20 or 30 metres off, for several seconds at a time. A threshold of 5 metres would buzz all the way through the woods while you are perfectly on the path.
The threshold is the size of the cloud you are willing to ignore. Ridge offers three:
| Threshold | Buzzes when | Best for |
|---|---|---|
| 15 m | You have taken the wrong fork within a few strides | Open terrain, alpine ridges, well-cleared paths where every fork matters |
| 25 m | You are clearly off, before the wrong path drags you far | The default. Most trails, most days |
| 40 m | You are unambiguously somewhere else | Dense forest, gorges, urban canyons, old GPX files drawn loosely |
You set it once in Ridge’s settings, and the watch uses it on every route.
Picking a number for your route
Two questions decide it.
How good is the sky? Ridge lines, plateaus, open hillsides: 15 or 25. Forest for most of the way, valley floors with cliffs on both sides: 40, or you will learn to ignore the tap, which is the one thing you must never do.
What does a wrong fork cost? On a race course where the wrong turn is 400 m of descent you have to climb back, 15 m pays for the odd false alarm. On a wide fire road with the next junction two kilometres away, 40 m is plenty.
If in doubt, leave 25 and adjust after one outing. Ridge records where you actually ran, so you can compare your line with the trace afterwards and see where you drifted.
What the GPX file itself brings
An alert is only as good as the trace it compares against.
- Hand-drawn routes in planning tools follow the path from the map database, which is usually within a few metres of the real path. Good.
- Recorded activities carry the GPS noise of the day they were run. Fine for the shape; the wobbles can cost you a false alarm under trees. 25 or 40.
- Simplified files with one point every 100 m cut corners on switchbacks: the straight line between two points can be 20 m inside the real bend. Ridge alerts against the line, so a hairpin can read as “off” for a moment. 40 m absorbs it.
What an alert cannot do
It cannot tell you which way the path went. The watch shows the trace and your dot; you read it. On a trail that is a two-second glance, and Ridge draws the trace big enough for it.
It cannot reroute you. There is no road network on a mountainside; the trace is the route. If you decide to shortcut, the alert will say so and then say “back on the trail” when you rejoin. That is a feature.
It is not a substitute for knowing the tricky spots. For those, pin a note on the route (“left fork is a dead end”, “cairns, not the obvious path”); it taps your wrist as you approach, before you can go wrong, rather than after.
In one line
Default 25 m. Go to 15 m when the sky is open and a wrong fork is expensive. Go to 40 m when trees or cliffs make the GPS wander. And never train yourself to ignore the tap: change the number instead.