Lesson 21: Set and Drift Problems

Use chart 12221, 9 degrees West Variation and the deviation table from Lesson 10-

1. At 1712 your loran set indicates a position of LAT 36°54.8'N, LONG 75°39.8'W. You are on course 319° per magnetic compass at a speed of 9.9 knots. At 1800 your loran set indicates your position at LAT 37°00.0'N, LONG 75°45.8'W. What were the set and drift?

A.087º T at 1.5 kt
B.267º T at 1.6 kt
C.262º T at 0.9 kt
D.093º T at 0.8 kt

1.Plot-label 1st Fix and note time
2.Plot-label DR Track Line in TRUE DEGRESS from 1st Fix, if given in degrees PMC work up to true
3.Plot-label 2nd Fix and note time
4.Determine number of minutes between fixes
5.Using D=(SXT)/60 solve for DR run distance, plot, and label it “DR”
6.Find SET in TRUE DEGRESS (DR2nd Fix)
7.Solve for DRIFT speed in knots S = (DX60)/T using distance in nm between DR and 2nd Fix.

2. At 1119 your position is 36º 59.0’ N 075º 29.0’ W on a course of 270º T at 10.5 kt. At 1220 your position is 36º 58.5’ N 075º 43.9’ W. What is the set and drift?

A.026º at 0.7 kt
B.046º at 1.0 kt
C.220º at 0.9 kt
D.245º at 1.4 kt

3. On a ship’s heading of 088º PMC at a speed of 9.5 kt the 0754 position is 37º 01.0’ N 075º 46.0’ W. The 0900 position is 37º 01.6’ N 075º 31.0’ W. What is the current?

A.122º T at 1.8 kt
B.100º T at 2.0 kt
C.273º T at 0.8 kt
D.295º T at 1.1 kt

4. At 0019 your position is 37º 00.0’ N 075º 30.0 W on a course of 270º T at 8.7 kt. At 0100 your position is 36º 59.7’ N 075º 37.05’ W. What is the set and drift?

A.137º T at 0.7 kt
B.150º T at 0.9 kt
C.331º T at 0.7 kt
D.347º T at 0.7 kt

5. At 1939 your GPS is 36º 56.0’ N 075º 42.0’ W on a course of 111º T at 12.8 kt. At 2000 your position is 36º 53.9’ N 075º 36.0’ W. What was the set and drift?

A.130º T at 0.9 kt
B.134º T at 2.1 kt
C. 091º T at 1.6 kt
D.103º T at 1.1 kt

6.What were the Course Made Good (CMG) and Speed Made Good (SMG) for problem number 5?

A.129º T, 2.0kt
B.112º T, 14.9kt
C.115º T, 13.0kt
D.129º T, 0.9kt




Answers:

1.A
2.D
3.A
4.A
5.B
6.B