Therefore, care must be taken whenever computing true wind data. Observing Wind Data . Wind data can be observed using the following methods. The order given is also the priority of use. Wind data observed from the speed and direction indicators of the installed anemometer.
Anemometers measure the apparent wind speed and indicate the apparent wind direction.
Use of a hand held anemometer. Visual estimation of the true wind direction and speed. Visual estimation should be used only when the installed and hand held anemometers are inoperative or not available. When the wind data is visually estimated the true wind speed and direction are directly derived. Never observe the wind while the ship is turning .