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Navegamos en demanda del Estrecho, se va haciendo Rs = 070º, se tiene viento del SW que abate una vez a rumbo 6º. Se marca en el Radar el faro de Cabo Espartel 45º. Calcular la demora de Cabo Espartel.Approaching the Strait making good surface course Rs = 070º with a SW wind causing 6º of leeway, you take a relative radar bearing of Cape Spartel = 45º (starboard). What is the true bearing (Dv) of Cape Spartel?
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Correct answer: c) Dv = 121º.
Why it is correct
A SW wind blows on the starboard side and pushes the vessel 6º to port (reducing the course angle), so to make good Rs = 070º the ship’s head is Rv = 070º + 6º = 076º. Since a radar relative bearing is measured from the ship’s head (Rv), Dv = Rv + M = 076º + 45º = 121º.
Why the others are not
- a) Fails to add the relative bearing to the true heading (Rv = 076º) rather than the surface course.
- b) Fails to add the relative bearing to the true heading (Rv = 076º) rather than the surface course.
- d) Fails to add the relative bearing to the true heading (Rv = 076º) rather than the surface course.
How to work it out in the exam
- Find the true heading of the bow: with a SW wind (6º leeway to port), Rv = Rs − Ab = 070º − (−6º) = 076º.
- Add the radar relative bearing to the true heading: Dv = Rv + M = 076º + 45º = 121º.
Where this question comes from
- Junta de Andalucía · 2015 · 3ª convocatoria · PY Módulo de navegación · question 20 Official paper · Official answer key
Try it: Navigation calculations
Pending instructor review. Machine translation, not reviewed.