The pebbles, explained

A point on the course that says “I was here, at this time”. The app takes your phone's GPS position and snaps it to the nearest point on the track.

It is not a check-in. A check-in is you officially confirming a checkpoint. A pebble can be dropped anywhere, between 2 aid stations, as often as you like. The two live separate lives: dropping a pebble after an aid station does not check you in there.

An orange “Drop a pebble” button floats at the bottom of the screen, on every tab. Big, round, thumb-reachable — designed for km 60, with gloves on, in the rain, and a brain running at half speed.

One press and it is done. The app confirms the distance mark, the button turns green for 6 seconds — in the rain, with gloves on, the only question is “did it go through?” —, and your crew gets a notification straight away. An automatic pebble has just dropped? Yours goes through anyway: it is precisely when the automatic tracking got it wrong that you press. Only an accidental double press is refused.

🪨 Pebble dropped at km 18.4

🪨 Drop a pebble🪨 …✓ Pebble dropped — km 18.4

📱 On your crew's phones

🪨 Camille #4218.4 / 100 km at 09:40 · 👥 Engreux around 11:20

In automatic mode, a pebble is dropped every time you open the app, then every 20 minutes for as long as it stays on screen. You do nothing: you check your next aid station, and your position leaves on its own.

Those pebbles are quiet: they update the map without sending a notification. Otherwise your crew would get an alert every 20 minutes for 15 hours, and would hate you before the finish.

It is set in Le Cairn, runner by runner: a 🪨 auto checkbox in the runners table. Some will want it, others won't.

Every pebble says where you are and at what time. The app measures the pace you have held since the last aid station, applies it to what is left before the next one, and shifts the whole rest of the race by the difference.

The planned durations between points are untouched: the climb at km 50 stays as long as announced. It is the time of day that slides, not the course.

Your crew and your family see exactly the same times, at the same moment. No need to ask: the arrival time at the next aid station is already up to date on their screen.

km 12 up a 15 % climb and km 12 along a flat path are not run at the same speed. Simple arithmetic on distance alone therefore announced nonsense on a mountainous leg, and got it wrong the other way on a descent.

The app now works in effort kilometres: it reads the elevation gain from the GPX track and converts it into distance. By default, 100 m of climb = 1 km more. A leg of 8 km with 400 m of climb is therefore worth 12 effort km.

At the start of a leg, the measurement is worthless. 500 m after an aid station, one toilet stop is enough to suggest you will take 6 hours to reach the next one. So the app starts from the plan, and lets the measurement take over gradually, up to 25 % of the leg. Past that quarter, only your real speed counts. The handover is smooth: no 20-minute jump as you cross a threshold.

Both settings — the 100 m and the 25 % — are changed in Le Cairn, runner by runner. A climber loses less on the ascents than a flat-ground runner: it is adjustable.

It happens to everyone: you cross the aid station, fill the bottles, set off again — and forget to check in. 3 hours later, the crew still thinks you are at km 30.

Now, if your pebbles show you have gone more than 1 km past a point without confirming it, the app asks you about it. It even suggests the estimated time you went through, worked out from the pebbles before and after: you confirm, and the imaginary delay disappears.

The other way round: when you confirm a checkpoint, your position lands on that aid station. No more runner shown 2 km before the point they have just checked into.

On an ultra you do not pass through an aid station: you sit down in it. From Le Cairn, every checkpoint now accepts minutes of stopped time — and every time that follows shifts by itself, all the way to the finish.

More importantly, the cut-off alert is compared to the time you leave the aid station, not the time you arrive. That is the race officials' rule: arriving 3 minutes before the cut-off is worth nothing if you need 15 minutes of soup before setting off again.

And for races lasting more than a day, cut-offs accept a day: D, D+1, D+2. A cut-off at 08:00 the next morning is finally understood as the 26th hour of racing — no more absurd times past midnight, or 2 days later.

And at life bases, a timer measures the real stop, next to the one your plan allows — it is in the pacing guide.

Every pebble leaves a dot on the map and on the altitude profile. Solid orange for the ones you dropped yourself, translucent grey for the automatic ones. At the finish, you get to read your race back.

And the map survives the dead zones: the map tiles you looked at the night before stay on the phone, and still show up in the mountains.

In the Crew and Public views, every runner has their own colour — you follow everyone at a glance without mixing them up.