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true_from_apparent

navcore_math::wind

Function true_from_apparent 

Source 
pub fn true_from_apparent(apparent: Wind, vessel_speed_kn: f64) -> Wind
Expand description

True wind from measured apparent wind and the vessel’s own motion.

This is the direction the instruments cannot measure: a masthead unit only ever sees apparent wind, and everything tactical is computed from what this returns.

Apparent wind is the vector sum of true wind and the vessel’s own velocity; this function subtracts the vessel’s velocity back out. For 15 kn of apparent wind at 40° and a vessel making 6 kn:

vessel 6 kn true wind 11.1 kn @ 60° apparent wind, 15 kn @ 40°