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General Duties of the QMOW, Continued
Example: The ordered course and speed is 080° at 10 knots. You have
just plotted the 1000 fix, which shows the ship right of track. What is
the set and drift? Refer to the following table and figure 11-8 to find
set and drift.
Step
1.
2.
3.
4.
Action
Find the CMG and SMG between the 0900 (A) and 1000 (C)
fixes. You can see the CMG = 089 and SMG = 11.2 kn.
Using a parallel ruler or PMP, find the direction between the
1000 DR (B) and the 1000 fix (C). As you can see, this equals
140°, the ship is being set in the direction of 140°
Using dividers, measure the distance between the 1000 DR (B)
and the 1000 fix (C). The distance is equal to 2.0 nmi.
To find drift, divide the distance by the time between the two
fixes. For our example the time between the two fixes is 1
hour. Drift equal 2.0/1.0 or 2.0 kn.
Note: You may measure set and drift over many hours, if
necessary. For example, if distance = 8.4 nmi, time = 7.5 hours
what is the drift? 8.4 + 7.5 = 1.12; drift equals 1.12 knots
Figure 11-8. Finding set and drift.
11-38
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