Navegamos al Rumbo verdadero 070º y velocidad del buque = 6 nudos, en zona de corriente desconocida. A HRB = 09:00 tomamos Marcación al faro de Punta Carnero = 090º BR (babor) y distancia = 6 millas. Al ser HRB = 10:30 tomamos Demora verdadera al faro de Punta Almina = 183º y distancia = 5,2 millas. Calcular Rumbo e Intensidad horaria de la corriente.Steaming on true course 070º at 6 knots in an unknown current, at HRB 09:00 Punta Carnero bears 090º Port at 6 miles, and at HRB 10:30 Punta Almina bears Dv = 183º at 5.2 miles. Calculate Rc and Ihc:

Correct answer: c) Rc = 225º Ihc = 2.8'

Why it is correct

At 09:00, with Rv = 070º and Carnero 090º Port relative, Dv(Carnero) = 070º − 90º = 340º (reciprocal 160º at 6′: 35º 58.7′ N, 005º 23.2′ W). In 1.5 hours (09:00 to 10:30) at 6 knots you run 9 miles along 070º to a DR at 36º 01.8′ N, 005º 12.8′ W. The 10:30 fix (5.2′ on 003º from Almina) is 35º 59.2′ N, 005º 16.2′ W. From DR to fix is 4.2′ towards 225º ⇒ Ihc = 4.2 / 1.5 = 2.8 knots.

Why the others are not

• a) Does not divide the 4.2-mile total drift by the 1.5 hours or reverses the current direction.
• b) Does not divide the 4.2-mile total drift by the 1.5 hours or reverses the current direction.
• d) Does not divide the 4.2-mile total drift by the 1.5 hours or reverses the current direction.

How to work it out in the exam

1. Plot the start (6′ on 160º from Carnero), lay off 9 miles along 070º for the DR and plot the fix (5.2′ on 003º from Almina).
2. Measure from DR to fix: Rc = 225º and drift = 4.2′ in 1.5 h ⇒ Ihc = 2.8 knots.

Where this question comes from

• Junta de Andalucía · 2026 · 2ª convocatoria · PY Módulo de navegación · question 16 Official paper · Official answer key

Try it: Navigation calculations

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