Polar percentage (POL)
The polar percentage compares the boat speed with its target speed at the same angle and wind. Computation, primary polar, recomputing sessions and interpretation.
The essentials
The polar percentage (POL) is the boat speed divided by the polar’s target speed, at the same true wind angle (TWA) and the same wind speed (TWS). At 100%, the boat exactly matches its polar.
- Each boat has a primary polar: it is the one used for the computation.
- At every moment, Avelsta interpolates the target speed in the polar and computes the percentage.
- The session shows its average POL in its header, in the session list and on the home screen; the timeline shows the “polar %” curve.
Going further
The computation
- The target speed is interpolated between the angles and wind speeds of the polar table.
- The angle is taken as an absolute value: starboard and port use the same polar.
- The speed compared is the one of the polar: STW (through water) or SOG (over ground).
- Dock time, GPS jumps and excluded ranges do not count.
Which polar for which session?
A session’s POL is computed with the boat’s primary polar at the time of computation, and the session records which polar it was.
| Event | Effect on POL |
|---|---|
| A boat’s first polar, or a new primary | Sessions with no polar are computed; the others keep theirs |
| A polar is edited (values or STW / SOG speed) | Sessions computed with it are recomputed |
| A polar is deleted | Its sessions are recomputed with the primary of the moment |
| New primary | The next sessions and imports use it; sessions already computed do not change |
Comparing with another polar
Without recomputing anything, a session page can compare the speed with another polar: the timeline’s Polars menu, or the selector of the Polar tab.
Interpreting the POL
| POL | Reading |
|---|---|
| Above 100% | The boat beats the polar: cautious polar, favourable current (in SOG), surfing, or wind readings to calibrate |
| 90 to 100% | Sailing close to the potential |
| 75 to 90% | Room for progress: trim, sail choice, helming |
| Below | Manoeuvre, rough sea, or a range to exclude (engine, waiting) |
The POL depends on the quality of the polar and of the sensors: a poorly calibrated wind sensor or log shifts everything.
Frequently asked questions
Why does my session have no POL?
The boat had no polar when it was computed. Add a polar to the boat: the session is recomputed automatically.
I changed the primary polar and my old sessions did not change
That is by design: a session keeps the polar it was computed with, so it stays comparable over time. To compare it with the new one, use the timeline’s Polars menu.