Understanding your stats
A guide to every number in the debrief — what it means, what to look for, and how to use it.
The debrief tool shows a range of stats to help you review a session. Some appear automatically; others only appear when wind direction or course marks are set. This page explains each one in plain language so you can get the most from your review.
All stats are derived from GPS and phone sensors. They are useful approximations — not exact measurements — and accuracy depends on conditions, phone hardware, and mounting.
Boat comparison
When multiple boats are loaded, the Stats tab shows a side-by-side comparison table. Each column is a boat; each row is a metric. Click a boat name to make it the primary (highlighted) boat.
p95 speed
The speed that the boat was at or below for 95% of the session. This filters out brief GPS spikes and gives a more reliable picture of sustained top-end speed than a raw maximum.
Max speed
The single highest speed recorded during the session. Useful as a reference point, but treat it with caution — GPS noise can produce occasional spikes.
Distance
Total distance sailed during the session (or active segment), measured in metres. Useful for comparing how much ground different boats covered in the same conditions.
PY handicap
Portsmouth Yardstick handicap values can be entered per boat in the Boats tab. When set, comparison metrics are scaled so boats of different classes can be compared on a level playing field. A PY of 1000 is the baseline — higher numbers mean slower classes.
Manoeuvres
Manoeuvre stats appear when a wind direction is set. The debrief detects tacks and gybes automatically from the track data.
Tack and gybe count
How many tacks and gybes the boat made during the session or segment. Useful for comparing workload and tactical choices between boats.
Average loss
The average distance lost per tack or gybe, measured in metres. "Loss" means: how much less ground you made toward the wind (or downwind) compared to if you had kept sailing in a straight line at a steady speed. A lower number means a cleaner, more efficient manoeuvre.
Best loss
The smallest loss recorded across all tacks (or gybes) in the session. This is your cleanest manoeuvre — the one to try to repeat.
Worst loss
The largest loss recorded. Often worth replaying in the debrief to understand what went wrong — was it hesitation, an overshoot, a wave, or traffic?
Manoeuvre detection requires a wind direction. If no wind is set, the manoeuvre section will not appear.
Live boat overlay
Toggle the live boat overlay in the Stats tab to see four real-time values for the selected boat as you scrub through the timeline.
Speed
The boat's speed over ground at the current playback time, shown in knots.
VMG
Velocity Made Good — the component of speed that is actually taking you toward (or away from) the wind. A boat sailing fast but at a poor angle might have a lower VMG than a slower boat on a better course. VMG only appears when a wind direction is set.
Heading
The direction the boat is pointing, shown as a three-digit compass bearing (e.g. 042°). Useful for checking consistency on a beat or comparing pointing angles between boats.
Heel
The side-to-side tilt of the boat, derived from the phone's accelerometer. Shown as a smoothed value to reduce noise. Useful for spotting patterns — consistent over-heeling on one tack, for example — but accuracy depends on phone placement.
Course analytics — legs
When buoys and wind are set in the Course tab, the debrief can break the session into legs (e.g. Start → Windward mark, Windward mark → Leeward mark). The Legs table in the Stats tab shows per-leg metrics for the selected boat.
Elapsed time
How long the boat took to complete the leg.
Distance
Total distance sailed during the leg — not the straight-line distance between marks, but the actual path taken.
Average speed
Mean speed over the leg, shown in knots. Combined with distance, this tells you whether a slow leg was caused by a longer path or genuinely lower boat speed.
CMG (Course Made Good)
The effective speed toward the next mark. If you sail fast but take a wide line, your CMG will be lower than a boat that sails a tighter course. A higher CMG means you're converting more of your speed into progress toward where you need to go.
Tacks / Gybes per leg
How many manoeuvres the boat made on each leg. Useful for comparing tactical approaches — did extra tacks gain or lose time?
Fleet best and delta
When multiple boats are loaded, each leg shows the fastest time across the fleet, who led that leg, and how far behind the selected boat was (in seconds). Colour-coded: green for small gaps, amber for moderate, red for large.
Course analytics — roundings
The Roundings tab shows how the selected boat approached and rounded each mark.
Tactical loss
How much extra distance the boat sailed approaching the mark compared to a direct approach. A high number suggests the boat took a wide or inefficient line into the rounding.
Clearance
The closest distance between the boat and the mark during the rounding. Very tight clearances suggest an aggressive approach; large clearances suggest the boat gave the mark too much room.
Actual vs expected distance
The actual distance sailed through the rounding zone compared to the expected (ideal) distance. The gap between these two numbers is the tactical loss — the metres that could have been saved with a cleaner approach.
Segments
Segments let you isolate a specific part of the session — a single race, a drill, or a particular beat. When a segment is active, all stats (comparison, manoeuvres, course analytics) are recalculated for that time window only. This makes it easier to compare specific moments rather than entire sessions.
Wind direction
Many stats depend on knowing the wind direction. You can set it in the Stats tab using the compass dial, or it may be included automatically in a coached session. Once wind is set, the debrief unlocks:
- Tack and gybe detection with loss calculations
- VMG in the live boat overlay
- CMG (course made good) in leg metrics
- Rounding loss analysis relative to the wind axis
If wind direction is not set, these stats will not appear. The remaining stats (speed, distance, heading, heel) work without wind.
Tips for reading the stats
- Look for patterns rather than single numbers — one bad tack is less important than consistently high tack loss
- Compare boats in the same conditions, not across different sessions
- Use segments to focus on a specific drill or race rather than the whole session
- A low CMG with high speed usually means a wide line — look at the track to confirm
- Stats are derived from GPS and phone sensors; treat them as useful approximations, not exact measurements
Next steps
Open one of the example sessions below to see these stats in action.
Questions about using the stats in your debriefs? Contact us at hello@dinghy.coach.