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A HRB = 12:00 tomamos demora verdadera al faro de Isla de Tarifa = 110º y demora verdadera al Fº de Pta. Alcázar = 145º. Una vez situados, damos rumbo al Puerto de Tánger (farola del espigón) con velocidad 8 nudos, teniendo en cuenta que existe una corriente con Rc = OESTE e Ihc = 3 millas. Declinación magnética = 8º NE y Desvío de la aguja = +4º (más). Calcular Rumbo de aguja a TángerAt HRB 12:00 you take Dv Isla de Tarifa = 110º and Dv Punta Alcázar = 145º, then head for Tangier port breakwater light at 8 knots in a current setting West at Ihc = 3 knots (variation 8º NE, deviation +4º). Find Ra to Tangier:
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Correct answer: a) 160º
Why it is correct
Intersecting Dv(Tarifa) = 110º and Dv(Alcázar) = 145º fixes the vessel at 36º 01.5′ N, 005º 42.6′ W. From there the effective course to Tangier breakwater is Ref = 198º. With a West current (Rc = 270º, Ihc = 3 knots) and Vb = 8 knots, the current triangle gives Rv = 172º. With Ct = +8º + 4º = +12º, the compass course is Ra = 172º − 12º = 160º.
Why the others are not
- b) Does not counteract the west-going current or fails to subtract total compass error Ct = +12º.
- c) Does not counteract the west-going current or fails to subtract total compass error Ct = +12º.
- d) Does not counteract the west-going current or fails to subtract total compass error Ct = +12º.
How to work it out in the exam
- Plot the intersection of Dv = 110º and 145º, draw Ref = 198º to Tangier and counteract Rc = 270º (3 kn) with Vb = 8 kn ⇒ Rv = 172º.
- Subtract Ct = +8º + 4º = +12º: Ra = 172º − 12º = 160º.
Where this question comes from
- Junta de Andalucía · 2016 · 3ª convocatoria · PY Módulo de navegación · question 13 Official paper · Official answer key
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Pending instructor review. Machine translation, not reviewed.