Metrics Reference

1. Wind & Speed Sources Priority

The analysis engine establishes reference axes according to strict data quality rules:

1. 01
   Wind source priority: 1. Observed wind (from on-site anemometer/weather stations); 2. Manual wind (entered by PRO for the session); 3. Inferred wind (calculated from fleet tacking course distribution). Inferred wind provides direction only; wind speed is never fabricated.
2. 02
   Missing wind fallbacks: when no usable wind reference exists, wind-dependent metrics (Wind-axis VMG, MMG, Loss) remain unavailable. Course VMG can still be computed using the bearing to the next course mark.
3. 03
   SOG & COG: SOG prioritizes device-recorded doppler speed, falling back to GPS-derived displacement. GPS course over ground (COG) represents movement, not bow heading.

2. Start & Leg Metric Specifications

1. 01
   Time to line (TTL): elapsed time in seconds from starting gun signal to the boat's bow crossing the line vector.
2. 02
   Signed distance to line: perpendicular distance to the starting line at the gun signal. Negative = behind the start line (safe); Positive = on the course side (potential OCS).
3. 03
   DMG30 & VMG30: net displacement toward mark 1 within the first 30 seconds after the gun. Negative progress is clipped to zero. Boats crossing after 30s receive zero. VMG30 = DMG30 / 30s.
4. 04
   Extra distance: actual sailed track length minus direct straight-line distance between marks, floored at zero. Extra distance % = Extra distance / Direct distance.

3. Maneuver Loss & Turn Bisector Axis

Maneuver Loss quantifies tactical efficiency during a tack or gybe against an objective straight-sailing baseline:

1. 01
   Maneuver axis: the turn bisector axis splits the entry course and exit course evenly, capturing true forward progress through the turn.
2. 02
   Baseline calculation: the straight-sailing speed is measured immediately before the maneuver window. Expected progress = baseline speed × maneuver window duration.
3. 03
   Loss formula: Loss = Expected progress - Actual net progress along the bisector. Negative Loss means gain against baseline; Positive Loss means progress lost in metres.
4. 04
   Recovery time: measured in seconds from the minimum apex speed until boat speed recovers to 85% of entry speed.

4. Why a 1 Hz Track Can Have an Incomplete Window

A maneuver normally requests 30 seconds before and 30 seconds after its center (60-second standard window). Even when every single second has a recorded GPS point, the window can be clipped:

1. 01
   Adjacent maneuver collision: when two tacks occur within 40 seconds of each other, the window must truncate to avoid counting the adjacent turn.
2. 02
   Mark rounding boundary: entering a mark rounding zone or passing the finish line terminates open-water maneuver windows.
3. 03
   Display behavior: incomplete windows (e.g. 41s or 57s) leave Loss and MMG blank (displaying a dash "-", not zero) with a tooltip explaining the clipping source.

5. Statistical Exclusion Criteria

To ensure fair leaderboards, maneuvers meeting any of the following criteria are excluded from fleet averages (displayed with an exclusion tag):

1. 01
   Window duration outside 15–85 seconds.
2. 02
   Entry or exit SOG below 0.8 knots (drifting or stalled boats).
3. 03
   Calculated Loss outside -40 m to +150 m range (extreme anomalies from anchor lines or collisions).
4. 04
   Turns within mark rounding zones (analyzed separately in Mark Rounding views).