DownwindTracker is a capture device for OC1 and surf ski paddlers. Your Apple Watch records 100 Hz IMU and 1 Hz GPS through the paddle, then transfers the session to your iPhone for upload and downwind analysis.
The app is intentionally narrow in scope: reliable capture and reliable delivery. All bump detection, dead-water identification, and coaching happens server-side, which means the watch app stays small, the phone app stays simple, and your data stays portable.
Apple Watch Ultra users can map it to the Action Button via StartPaddleIntent.
The app opens a HealthKit workout session so the watch keeps recording in the background.
When you end the recording, the watch packages two CSVs (accelerometer and GPS) plus metadata (duration, sample count, observed Hz, SHA-256 checksums, dropped sample counts) and transfers them over WatchConnectivity.
Sign in once with a Supabase magic link. Sessions sync to the Downwind Cloud API (certificate-pinned HTTPS). After analysis you get bumps, dead-water sections, best 60-second average speed, and a coaching summary.
Transparent by design. Here is exactly what each session contains.
time, seconds_elapsed, x, y, zRaw 3-axis acceleration in the device frame at ~100 Hz. Nanosecond epoch timestamps.
time, seconds_elapsed, latitude, longitude,
ellipsoidalAltitude, altitude, course, speed,
verticalAccuracy, horizontalAccuracy,
speedAccuracy, courseAccuracyCore Location output at ~1 Hz. Speed in meters per second; backend normalizes units.
The watch never uploads directly. The phone is the only client that talks to the backend, and only when you press upload.
Bump detection, dead-water identification, and coaching are computationally non-trivial and benefit from frequent iteration. Keeping the watch and phone scope narrow means the analysis engine can improve without forcing app updates, and your raw sensor data is always reprocessable against newer models.
No, but the Action Button integration (one-press start from the wrist) requires Apple Watch Ultra. Standard Apple Watch models running watchOS 26.2 or later can still record sessions from the in-app start screen.
The app is built for OC1 outrigger canoe and surf ski downwind sessions. The capture format is sport-agnostic, so V1, V6, SUP downwind, and other paddle disciplines will record correctly; the analysis is tuned specifically for ocean downwind bump-running.
Auth is handled by Supabase using magic-link email sign-in. Sessions upload to the Downwind Cloud API over certificate-pinned HTTPS. See the Privacy Policy for full detail.
The app is currently in TestFlight beta. There is no committed App Store launch date yet. Email support@downwindtracker.com to request TestFlight access.
DownwindTracker is built and maintained by one person. Emails are answered directly.
support@downwindtracker.com