Set And Drift Formula

At 1200H you fix your position and change course to 315°T. At 1225H, you again fix your position, and it is 0.9 mile southwest of your DR position. Which statement is true?

Given:
1200H - Time of ship's first position
1225H - Time of ship's second position
0.9 miles - Distance between fix and DR position

What is asked:
1. Drift
2. Current Set

Solution:
This is the formula for ship's drift: Drift = (Distance/Time) x 60

Step 1. Get first the time interval.
           TI = 1225H - 1200H = 25 mins

Step 2. Divide the distnce by time interval.
                      0.9 miles ÷ 25 mins = 0.036

Step 3. Multiply the answer of step 2 by 60 to convert it into knots.
                     0.036 x 60 = 2.16 knots is the speed of drift.

For getting the set of current you can just determine it by analyzing the problem. The problem says that your second fix position is "0.9 mile southwest of your DR position". Your keyword here is "southwest". Since southwest is equivalent to 225°, therefore the set of current is 225°.

Set and Drift Formula

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