Clubhouse (base station)

• Runs from the clubhouse ashore, or from the committee boat — no shore site needed.
• Either way it is a fixed GNSS receiver on a surveyed position.
• It knows its own coordinate, so it can measure live satellite error: ionospheric drift, clock and orbit.
• Broadcasts that correction to every boat on the course.

Corrections

• One correction, sent continuously to every device.
• Comes from whichever base station is in use that day — the clubhouse, or the alternate on the committee boat.
• The whole fleet measured against a single reference.
• Errors cancel instead of compounding.
• Two boats side by side read the same distance to the line.

Start boat (alternate base station)

• Starboard end of the line, fixed by a corrected GNSS position.
• Can carry an alternate base station — mount it here and no shore site is needed.
• Ashore or afloat, the correction the fleet receives is identical.
• Recorded once. No transit to sight, no eyeballing the pin.
• Every boat races against the same coordinate.

Pin

• Port end, pinged the same way.
• Two surveyed endpoints define the line as a geodesic.
• The line the app draws is the line the committee set — bias included.

The line

• One line, defined once, shared by the whole fleet.
• Distance measured perpendicular from your bow, not your phone.
• Offset for where the mount sits on the boat.
• Sub-metre resolution: on the line or over it is measurable, not arguable.
• OCS is detected, not disputed — boats over early are flagged automatically.

Windward mark

• Set from the support vessel, published the moment it is dropped.
• Move the mark and the course updates on the water.
• No VHF call. No confusion about which mark is live.

The fleet

• One synchronised start sequence across the fleet.
• Timing disciplined against GNSS time, not the handset clock.
• Every device counts down to the same instant, whatever the network.

Support vessel

• Lays and moves marks; coordinates captured on the spot and published.
• Its own position is live on the same map.
• Every boat on the water is tracked.
• A capsize, a stopped boat or an alert shows up with a position to steer to.
• The crew sees it without waiting for a call from shore.

Coach boat

• Watches the race live with every boat's track on screen.
• Approach angles, timing on the line, tack-by-tack gains up the beat.
• Debrief on the water, while it still means something.
• Pre-race start practice: set a line, run sequences, review who was early or late.

On the boat

• Runs on the phone you already own, in a class-approved mount.
• Fixed, known position on the boat with an unobstructed view of the sky.
• Clean satellite fix and a consistent reference for every measurement.

Racing

• Live distance to line, time to burn, laylines and course position.
• Every fix logged as you sail.
• Replays afterwards at the accuracy it was recorded.
• Start approach, first cross, every gain and loss up the beat.