Apparent wind speed (AWS)
The speed of the wind in knots that we measure from a moving vessel. It is a
combination of the true wind speed and the effective wind we create with our
motion. Motoring at 8 kts straight into a 12-kt true wind, we would experience an
apparent wind speed of 20 kts. Sailing dead downwind at 7 kts in a true wind of
12 kt, the apparent wind would be reduced to 5 kt. When sailing diagonal to the
true wind direction, up or down wind, the resulting apparent wind speed cannot be
determined from simple arithmetic, but instead vectors must be solved as done by
this computer program. In general, though, sailing into the wind, the apparent
wind speed is always higher than the true wind speed and sailing downwind it is
always lower.