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Al encontrarnos al Sur verdadero del faro de Pta. Camarinal, marcamos el faro de la lsla de Tarifa en demora verdadera = 070º. Situados, damos rumbo a Barbate (faro de tierra), a 7 nudos de velocidad y teniendo en cuenta una corriente de Rc = SW e Ihc = 3 millas. Declinación magnética = 4º NE y desvío de la aguja = +8º (más). Calcular el rumbo de aguja a Barbate.When due South true of Punta Camarinal lighthouse with Isla de Tarifa lighthouse bearing Dv = 070º, you head for Barbate landfall light at 7 knots in a SW current of Ihc = 3 knots (variation 4º NE, deviation +8º). Find Ra:
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Correct answer: a) Ra = 350º
Why it is correct
The intersection of the Punta Camarinal meridian (005º 47.9′ W) with Dv(Tarifa) = 070º (reciprocal 250º) fixes the vessel at 35º 56.6′ N, 005º 47.9′ W. From there the effective course to Barbate is Ref = 338º. With a SW current (225º, 3 knots) and Vb = 7 knots, the current triangle gives Rv = 002º. With Ct = +4º + 8º = +12º, Ra = 002º − 12º = 350º.
Why the others are not
- b) Does not counteract the SW current to Rv = 002º or fails to subtract total compass error Ct = +12º.
- c) Does not counteract the SW current to Rv = 002º or fails to subtract total compass error Ct = +12º.
- d) Does not counteract the SW current to Rv = 002º or fails to subtract total compass error Ct = +12º.
How to work it out in the exam
- Plot the start (S of Camarinal with Dv Tarifa = 070º), draw Ref = 338º to Barbate and counteract Rc = 225º (3 kn) with Vb = 7 kn ⇒ Rv = 002º.
- Subtract Ct = +4º + 8º = +12º: Ra = 002º − 12º = 350º.
Where this question comes from
- Junta de Andalucía · 2020 · 3ª convocatoria · PY Módulo de navegación · question 17 Official paper · Official answer key
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Pending instructor review. Machine translation, not reviewed.