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A HRB = 09:00 nos encontramos en la oposición de los faros de Isla de Tarifa y Punta Cires y al Norte verdadero del faro de Punta Alcázar. Navegamos a 8 nudos al rumbo verdadero = 270º en zona de corriente desconocida. A HRB = 10:31 tomamos demora verdadera al faro de Punta Camarinal = 343º y demora verdadera al faro de Punta Cires = 091º. Calcular el Rumbo y la intensidad de la corriente.At HRB 09:00 on the Isla de Tarifa–Punta Cires opposition and due North true of Punta Alcázar, you steer Rv = 270º at 8 knots; at HRB 10:31 Dv Camarinal = 343º and Dv Cires = 091º. Find Rc and Ihc:
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Correct answer: a) Rc = 135º; Ihc = 3.0'
Why it is correct
The start (Tarifa–Cires opposition due N of Alcázar) is 35º 56.4′ N, 005º 33.4′ W. In 1h 31m (~1.5 h) at 8 knots along Rv = 270º the DR (12.1′ West) is at 35º 56.4′ N, 005º 48.3′ W. Intersecting Dv(Camarinal) = 343º and Dv(Cires) = 091º fixes the vessel at 35º 53.2′ N, 005º 44.4′ W. From DR to fix is 4.5 miles towards 135º ⇒ Ihc = 4.5 / 1.5 = 3.0 knots.
Why the others are not
- b) Does not divide the 4.5-mile drift by the 1.5 hours or reverses the current direction.
- c) Does not divide the 4.5-mile drift by the 1.5 hours or reverses the current direction.
- d) Does not divide the 4.5-mile drift by the 1.5 hours or reverses the current direction.
How to work it out in the exam
- Plot the DR (12.1′ W of the start) and the observed fix (Dv Camarinal = 343º, Dv Cires = 091º).
- Measure from DR to fix: Rc = 135º and d = 4.5′ in 1.5 h ⇒ Ihc = 3.0 knots.
Where this question comes from
- Junta de Andalucía · 2024 · 1ª convocatoria · PY Módulo de navegación · question 17 Official paper · Official answer key
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Pending instructor review. Machine translation, not reviewed.