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El día 1 de abril de 2021 a HRB: 02:20 nos encontramos en situación 36º03,0'N 006º05,7W navegando al Rumbo de Aguja 134º con un Desvío de 7,5º(-) y una Declinación Magnética de 3,5º(-), la velocidad de máquinas es 10 nudos. Situados, entramos en una zona de corriente desconocida. A HRB: 03:35 tomamos Demora de Aguja al Faro de Cabo Espartel de 222º y una Demora de Aguja al Faro de Punta Malabata de 163º. ¿Qué Rumbo e Intensidad Horaria de la Corriente se aproxima más a la que nos afecta?On 1 April 2021 at 02:20 in 36º 03.0' N, 006º 05.7' W on Ra = 134º (deviation –7.5º, variation –3.5º) at 10 knots, you enter an unknown current; at 03:35 Da Spartel = 222º and Da Malabata = 163º. Find the current's set and drift:

Show the answer

Correct answer: a) Rc = 095º; Ihc = 2.3 knots.

Why it is correct

With Ct = −3.5º − 7.5º = −11º, true heading is Rv = 134º − 11º = 123º. In 1h 15m (1.25 h) at 10 knots, DR (12.5′ on 123º) reaches 35º 56.2′ N, 005º 52.8′ W. At 03:35, Dv(Spartel) = 211º and Dv(Malabata) = 152º fix the vessel at 35º 55.9′ N, 005º 49.3′ W. The vector from DR to fix is 2.9′ towards 095º ⇒ drift = 2.9 / 1.25 = 2.3 knots.

Why the others are not

  • b) Does not divide the 2.9-mile total drift by the 1.25 hours elapsed or reverses the direction.
  • c) Does not divide the 2.9-mile total drift by the 1.25 hours elapsed or reverses the direction.
  • d) Does not divide the 2.9-mile total drift by the 1.25 hours elapsed or reverses the direction.

How to work it out in the exam

  1. Plot 12.5 miles along Rv = 123º for the 03:35 DR and fix the observed position with Dv = 211º and 152º.
  2. Measure from DR to fix: Rc = 095º and drift = 2.9′ in 1.25 h ⇒ Ihc = 2.3 knots.

Where this question comes from

Try it: Navigation calculations

Pending instructor review. Machine translation, not reviewed.