The wind anemometer is a helicoid propeller type with a vane for direction measurement.
The wind anemometer is mounted in the forward mast which follows the general rule that anemometers should be placed as high and far ahead as possible in the ship, Yelland et al. (2002), to be free of distortion of the airflow to the anemometer.
The measuring accuracy is in the order of +/- 0.3 m/s or 1% of the wind speed and +/- 3° of the wind direction, Young (2010).
The accuracy is given to the range in which the anemometer is calibrated.
The relative wind speeds are distributed in the interval of 8 to 16 m/s.
Considering an overweight of head winds and the placement of the sensor in the forward mast, the wind measurements are subject to little distortion of airflow, which should lead to reliable measurements, Yelland et al. (2002).
The anemometer measures the relative wind speed and direction.
In the logging system on board the ship, this is converted to a true wind speed and direction.
To convert from true to relative measurements, there are relations to be used.