Concepts

How the World Wide Yacht Squadron measures a race - written for sailors who already know their way around a start sequence and a handicap fleet, not as a beginner's glossary.

Tack/gybe time lost

Every heading change through the no-go zone (tacking) or by the lee (gybing) costs some distance made good while the boat is turning and re-accelerating. The World Wide Yacht Squadron measures that cost directly from the recorded track rather than estimating it from a table:

1. The track is scanned for stable straight-line segments - a run of points on one side of the wind axis, upwind or downwind. A turn between two stable segments is a tack (upwind side flips) or a gybe (downwind side flips); short, noisy stretches around the turn itself are excluded, not treated as a segment.
2. The line the boat was sailing before the turn is extended forward, and the line it settled onto after the turn is extended backward, to find where the two lines cross.
3. Time lost is the difference between the boat's actual arrival time at its post-turn position and the hypothetical time it would have arrived there with no turn: sailing straight to the crossing point at the pre-turn speed, turning instantly, then sailing on at the post-turn speed.

Wind direction for classifying upwind/downwind and picking the tack/gybe side comes from whichever wind reading was in effect at each point's timestamp - for a replay, that's the reading that was actually current at the time, not today's wind. Time-lost figures and turn angles show up on a track's Stats view and as labels on the map for any tack/gybe in roughly the last minute.

Corrected time and sailed handicap

Results are scored by PHRF corrected time, the standard handicap-racing formula:

Corrected Time = Elapsed Time − (PHRF Rating × Distance)

PHRF Rating is in seconds per nautical mile (a slower boat carries a higher number, so more time gets subtracted); Distance is the course length actually sailed, in nautical miles. Within a division - or the race's overall group, scored the same way - the boat with the lowest corrected time wins, and every other boat is ranked against it.

The World Wide Yacht Squadron also reports each boat's sailed PHRF: the rating it would have needed, at the distance actually sailed, to tie the winner's corrected time exactly.

Sailed PHRF = (Elapsed Time − Winner's Corrected Time) / Distance

A sailed PHRF lower than a boat's rated handicap means it beat its rating that day; higher means it sailed slower than its rating predicts. The winner's own sailed PHRF always comes out equal to its rated handicap, by construction.

Asynchronous racing against ghost boats

A race here isn't limited to boats on the water at the same time. Every entry has its own independent start time - the same mechanism a pursuit start already uses for its staggered starts - so entries can start minutes, hours, or days apart and still be racing the same course. Once a boat's track is recorded, it becomes a ghost: anyone racing the same course later can see where that boat was at a chosen moment, replayed from its actual recorded positions.

Ghost positions are shown in one of two modes:

• Same time - the ghost is shown at the same elapsed time since its own start that you are currently at since yours. Straightforward apples-to-apples if the boats are evenly matched.
• Handicap - the ghost is shown at whatever elapsed time gives it the same corrected time you currently have, so a slower-rated ghost appears further back and a faster-rated one further ahead, adjusted for the distance you've actually sailed so far:

Ghost Elapsed = Your Elapsed + (Ghost's PHRF − Your PHRF) × Your Distance Sailed

This is the same CT = ET − PHRF × Distance relationship used for results, solved for the ghost's elapsed time instead of a corrected time - it answers "where would this ghost be right now if it were exactly tied with me on corrected time." If a ghost hasn't started yet, or already finished before the target elapsed time, it's simply shown at its start (not yet appeared) or frozen at its finish, rather than extrapolated further.

Wind readings

Tack/gybe detection needs to know which way the wind was blowing. Two sources feed it, in priority order:

1. Manual entry - a sailor or race committee logs current direction/speed during a race. This is authoritative whenever a reading exists from the last 15 minutes.
2. Weather-API fallback - if no manual reading that recent exists, the World Wide Yacht Squadron pulls current conditions from a marine weather service for the location, so tack/gybe detection keeps working with no manual input required.

Each reading is timestamped, so replaying an older track uses whatever wind was actually in effect at that point in time - not today's conditions.