A ship steaming on a course of 246° T at 17 knots. At 2107 a lighthouse was observed bearing 207 deg T and at 2119 the same lighthouse bears 179° T. What is the ship's distance off at second bearing?
SOLUTION:
Step 1. We have to get the angle at first and second observation. That is we to have subtract our course by the observed bearings.
SOLUTION:
Step 1. We have to get the angle at first and second observation. That is we to have subtract our course by the observed bearings.
- 246° - 207° = 39° as our angle at first observation (<A)
- 246° - 179° = 67° as our angle at first observation (<B)
Step 2. We have to get the time interval by subtracting time at first and second observation.
- 2119H - 2107H = 12 mins
Step 3. Multiply the answer of step 2 by ship's speed & then divide by 60.
- (12 mins x 17 knots) ÷ 60 = 3.4 miles
Step 4. Multiply the answer of step 3 by Sin <A.
- 3.4 x Sin 39° = 2.14
Step 5. Divide answer of step 4 by the difference of angle A and angle B
- 2.14 ÷ Sin 28° = 4.56 miles... is the ship's distance off at 2nd bearing.