tack.coach turns any sailor's phone into a centimetre-accurate tracker — then turns the track into a debrief a twelve-year-old can read and a coach can dig into.
One boat practising alone or a full squad — live tracking, wind and water quality, one screen after every session.
No sign-up to look around · the demo runs on invented boats · Android APK
±30 cm is post-processed (PPK) horizontal accuracy against the national GNSS reference network on supported phones — and only on a fix we trust: every solution is cross-checked against a second reference station and a stability gate, and a confident-but-wrong fix is rejected, not reported. Height is looser (a few times horizontal — every satellite sits above you). Live on-water positions are metre-class and device-dependent, then corrected for the debrief.
Fleet tracking used to mean buying hardware or hiring a crew for one big weekend. Starting from the phones your sailors already carry changes the economics — and who gets to use it.
Hardware trackers cost €500+ per boat before your first session. Here the tracker is the phone already in the sailor's drybag — adding a boat costs nothing.
Tracks are PPK-corrected against a national GNSS reference network to about ±30 cm horizontal — tight enough to score a tack in metres, not impressions. We only quote fixes that pass our trust check; the rest we flag rather than dress up.
A phone on a buoy is a mark, a wind station and a water-quality probe at once. The wind in your debrief comes from where you actually sailed, not the nearest airport.
Every session opens with a plain verdict — where you gained, where you gave it away — and only then the VMG plots, laylines and roundings for the coach.
Other tracking systems only make sense for big events. tack.coach runs itself for a solo sailor or a 5-boat Tuesday session just as happily as a full squad — no crew, no minimum.
Your sailors' tracks live on EU servers and belong to your club. Access is per person and revocable; nothing is public except the synthetic demo.
Three things happen after every session. Each one opens from a single screen, then goes as deep as the coach needs.
Open a boat and the moving track walks you through every tack — where you gained, where you gave it away. Tap deeper for VMG, laylines and per-leg made-good.
Drop virtual marks or turn a phone into a buoy to practise rounding. Then see exactly how each sailor took the mark — inside, wide, early or late.
A phone or a small Arduino station on a mark streams local wind and water quality straight into the debrief — so the numbers reflect the day you actually sailed.
Clip a phone and a webcam to a boat, the coach RIB, or a mark, and the live feed sits right on the tracked boat — tap it to watch, float it over the map to keep an eye on the fleet at the same time. The trainer sees the tack and the hiking that cost it.
Coming next: an on-the-water AI second opinion — a quick read of heel, crew and sail trim on the video, pinned to the moment on your replay.
An anchored phone becomes course infrastructure — a mark that knows exactly where it is, and a weather station reporting the breeze you actually trained in. Included from the free tier up.
Set a phone — or a virtual pin — as a course mark. It shows live on every screen and follows the real buoy if it drags. The group rounds it, and the debrief scores each rounding: inside or wide, early or late, and the metres it cost.
Add a wind sensor to the same buoy and local wind speed and direction stream straight into the debrief — so VMG, laylines and tack calls use the breeze on the course, not the airport forecast.
Our own buoy-mounted wind sensor, built to pair with a buoy phone out of the box — no configuration, readings flow into the live map and debrief automatically. Rated for lakes, lagoons and sheltered inland water; a salt-water housing is on the roadmap. Ships from November.
comparable Bluetooth wind meters run €300–500 — and don't feed your debrief
Not every phone earns the ±30 cm claim, and we won't pretend otherwise. What decides it is the GNSS hardware inside: raw measurements and the dual-band L5 signal. A phone with both reprocesses to ~±30 cm horizontal; without L5 it still lands well under a boat length; without usable raw output you get good, honest GPS — the debrief works at every tier, with error bars to match. And a fix has to earn our trust: two phones side by side can both report "locked" while one is quietly metres off, so we cross-check every solution and drop the ones that don't hold up. Some phones we recommend for buoy duty, a few we specifically don't.
The app reads your GNSS hardware directly — satellites, signal, L5, raw output — in two minutes on the dock. The guide shows what we measured across 25 real phones.
Every tier gets the same GPS accuracy and the same debrief. Paid tiers add fleet size and a faster AI onboard camera — a phone films the sail, and the AI reads trim, heel and trouble for the coach, live.
For a solo sailor — or a coach with a small group. Real tracking, real debrief, no card.
For a club or school running group sessions all season. €190/year — 2 months free.
For a sailing school with several squads and its own conditions data. €490/year.
Pay per boat, per race day — no tracker crates to ship, no chargers to collect. Live public viewer for parents on shore, course marks from buoy phones, and a PPK-reprocessed track for every entrant the same evening. Need the AI camera at a fixed rate for the jury or the livestream? The race package reserves capacity — the only tier where the cadence is guaranteed, not typical.
min €50 · capped at €150/day — a 50-boat, 2-day regatta is €200 flat. Guaranteed-cadence AI camera: priced per event.
About the AI camera rates, honestly: analysis runs on shared GPUs, so "~20 s" and "~8 s" are typical rates, not promises — on an unexpectedly crowded day every boat still gets analysed, just a little less often, and the boat a coach is actually watching always gets the fastest rate first. If your event needs a fixed cadence in writing, that exists — as the reserved-capacity race package above.
Where we sit, honestly: top-end instrument systems deliver 1 cm live positioning for umpired starts — at $1,249 per boat plus a corrections subscription. Rented-tracker event services run €450–€1,850 per event. If your programme needs that precision and timing, buy it. For everyone else, tack.coach delivers coaching-grade evidence from equipment your sailors already carry — Club is €19/month, events €2 per boat per day.
The demo is a synthetic session — invented boats, invented sailors, a generic bay. Scrub the replay, open a debrief, round the marks, read the wind. Everything works.
No real student's track is ever shown to anyone who isn't logged in. The public demo and the private data are different worlds — there is nothing here to scrape.
No password to invent — you'll sign in with Google once we've added you. A human reads every request.
A real session opens only for a signed-in coach who belongs to that club. Unknown accounts are turned away at the door.
Everything a visitor can reach is invented data on a generic bay. There is no real track to harvest — nothing to scrape.
You decide who joins your club's workspace. Access is granted per person, and you can revoke it any time. Hosted in the EU.
Real water, real weather, real numbers — from the sailors' own phones.