Appendix A Sailing Glossary - Raymarine ALPHA Operating Instructions Manual

Appendix A Sailing glossary

Below is a list of common terms and abbreviations used in sailing.
Term Meaning
Apparent Wind
The wind flow observed when in motion. Apparent
wind is different from True wind in that it takes
into account your own movement, i.e.: speed and
direction of travel. Apparent wind is the raw data
that is reported by wind transducers, which can
then be used in conjunction with other data sources
to calculate True wind.
Supported data:
• NMEA 2000: PGN 130306
• NMEA 0183: MWV
Apparent Wind The wind angle observed when in motion. AWA is a
Angle (AWA) combination of the true angle of the wind and the
angle that is felt due to direction and speed of travel.
Apparent Wind The wind speed observed when in motion. AWS is
Speed (AWS) a combination of the true speed of the wind and the
speed you are travelling.
Distance to Tack The travel distance remaining until you need to tack.
Distance to Line Distance remaining to the closest point along the
race start line.
Downwind Moving in the direction that the wind is blowing..
Ground Wind The direction of the wind relative to north, as
Direction (GWD) observed on land. This is the actual direction the
wind is blowing.
In addition to AWA, COG from a GNSS receiver is
also required to calculate GWD.
Ground Wind Speed The wind speed observed when stationary, as
observed on land. GWS is the actual speed the
(GWS)
wind is blowing over land.
In addition to AWS, SOG from a GNSS receiver is
also required to calculate GWS.
Sailing glossary
Term
Meaning
Header A wind shift which causes your boat to turn more
downwind.
Laylines Vector lines showing the course the boat will take
when sailing at the optimum angle to the wind, on
either tack.
Leeway The difference in angle between desired heading
and actual course, caused by sideways movement
of a sailing boat due to the wind.
Lift A wind shift which allows your boat to turn upwind
and closer to your destination.
Line bias The distance advantage conferred by crossing the
start line at the favored end. of the race start line.
Polar table
A performance profile for a boat, showing the boat
speed achievable at varying angles to the wind, with
varying wind speed. In sailing, the Velocity Made
Good (VMG) principle demonstrates that travelling
in a straight line is not always the quickest route,
and polars enable you to optimize your vessel's
performance to its best advantage, by improving
the accuracy of laylines to display how far you
need to sail on a current tack to reach a target
waypoint after tacking, and taking wind conditions
into consideration.
RSW (Raymarine The Raymarine Smart Wind transducer series. The
Smart Wind) RSW series of transducers include a built-in attitude
sensor which is used to provide more accurate
readings than standard wind transducers.
Sail plan Sail configuration recommendations based on wind
conditions.
Sailing upwind Sailing as close as possible to the wind direction.
Tack A course change made by a sailing vessel, b y
turning its heading into and through the wind.
Tacking The zig-zag manoeuvre a sailing vessel makes
when travelling upwind.
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