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A HRB = 21-45 se está en la oposición Fº de Isla Tarifa-Fº de Pta. Alcázar y a 5 millas de Pta. Alcázar, se pone Rv = 070º, Vhb = 6 nudos, hay corriente Rc = 095º Ihc = 3 nudos. Calcular la distancia a Pta. Europa al cortar la oposición Pta.Europa - Pta.Almina.At HRB 21-45 on the Isla Tarifa–Punta Alcázar opposition at 5 miles from Punta Alcázar, you steer Rv = 070º at Vhb = 6 knots in a current setting Rc = 095º at Ihc = 3 knots. Find your distance off Punta Europa when crossing the Punta Europa–Punta Almina opposition:

Show the answer

Correct answer: a) Dist = 8.2 miles.

Why it is correct

At 5 miles from Punta Alcázar on the Tarifa opposition we are at 35º 55.5′ N, 005º 34.9′ W. Vector-adding the vessel (Rv = 070º, 6 knots) and the current (Rc = 095º, 3 knots) yields effective course Ref = 078º. Plotting Ref = 078º to intersect the Punta Europa–Punta Almina opposition line, the distance from that intersection to Punta Europa lighthouse is 8.2 miles.

Why the others are not

  • b) Does not plot the effective track Ref = 078º resulting from combining (070º, 6 kn) and (095º, 3 kn).
  • c) Does not plot the effective track Ref = 078º resulting from combining (070º, 6 kn) and (095º, 3 kn).
  • d) Does not plot the effective track Ref = 078º resulting from combining (070º, 6 kn) and (095º, 3 kn).

How to work it out in the exam

  1. Plot the start and add the ship (070º, 6 kn) and current (095º, 3 kn) vectors ⇒ Ref = 078º.
  2. Intersect Ref = 078º with the Europa–Almina opposition and measure the distance to Punta Europa: 8.2 miles.

Where this question comes from

Try it: Navigation calculations

Pending instructor review. Machine translation, not reviewed.