MMC Upgrade Chart Plotting Practice Questions

Sample questions — Chart Plotting

Drawn from the same bank used on USCG licensing exams. Correct answers and explanations are shown — read every explanation, even for questions you get right.

1. 1. On a Mercator chart, one nautical mile is measured using the:

   • A.Latitude scale at the side of the chart, at the boat's approximate latitude✓
   • B.Longitude scale at the top or bottom of the chart
   • C.Bar scale only, regardless of latitude
   • D.Distance between meridians at the equator

   Why: One minute of latitude equals one nautical mile, so distance is read from the latitude scale on the sides. Because the Mercator latitude scale expands toward the poles, always measure at the mid-latitude of the leg, never on the longitude scale.

2. 2. When converting a true course to a compass course, westerly variation and deviation are:

   • A.Subtracted
   • B.Added✓
   • C.Ignored
   • D.Doubled

   Why: Going from true to compass (down the TVMDC sequence) you 'add west.' Westerly variation and deviation are added; easterly errors are subtracted. The mnemonic 'True Virgins Make Dull Companions — Add Whiskey' tracks the order and the add-west rule.

3. 3. A 'fix' is best defined as:

   • A.The intersection of two or more simultaneous lines of position✓
   • B.An estimated position from one bearing
   • C.A position derived from course and speed alone
   • D.The vessel's charted destination

   Why: A fix is the intersection of two or more lines of position taken at (or reduced to) the same time. A single LOP only narrows the position to a line; crossing two or more LOPs pins it down.

4. 4. To find the actual depth of water at a given time, you:

   • A.Subtract the height of tide from the charted depth
   • B.Add the bridge clearance to the sounding
   • C.Use the charted depth alone
   • D.Add the height of tide to the charted depth (sounding)✓

   Why: Charted soundings are referenced to a low-water datum (MLLW), so the real depth equals the charted sounding plus the predicted height of tide. At a negative (minus) tide, the actual depth can be less than charted.

5. 5. The 'bow and beam' bearing technique gives you, at the moment the object is abeam:

   • A.Your speed over the ground
   • B.Your compass deviation
   • C.The set of the current
   • D.The distance run between the bearings, which equals the distance off when abeam✓

   Why: Taking a bearing 45° on the bow and again at 90° (abeam), the distance run between the two bearings equals the distance off the object when it is abeam. It is a special case of doubling the angle on the bow.

6. 6. A line of position obtained from a single radar range to a charted object plots as:

   • A.A straight line through the object
   • B.A bearing line from the vessel
   • C.A point at the object
   • D.An arc (circle) of that radius centered on the object✓

   Why: A measured range places you somewhere on a circle of that radius around the object, so the LOP is an arc. Radar range LOPs are generally more accurate than radar bearings; crossing a range arc with a bearing or a second range yields a fix.

7. 7. A vessel is steering 090°T with 5° of leeway to leeward (wind from the north). What is the vessel's course through the water?

   • A.085°T
   • B.095°T✓
   • C.090°T
   • D.080°T

   Why: Leeway sets a vessel to leeward (downwind) of its heading, by the leeway angle, regardless of hemisphere (Bowditch). Wind from the north pushes the vessel southward; on a 090°T heading, south lies to starboard, so the course through the water = 090° + 5° = 095°T.

8. 8. A vessel steers 000°T at 10 knots in a 2-knot current setting 090°T. After one hour, what is the approximate Course Made Good?

   • A.000°T
   • B.011°T✓
   • C.349°T
   • D.090°T

   Why: The vessel travels 10 nm north and the current pushes it 2 nm east. Using vector addition, CMG = arctan(2/10) ≈ 011°T. The resultant track is slightly east of north due to the easterly current.

9. 9. Which of the following factors most significantly affects the amount of leeway a vessel experiences?

   • A.The depth of water under the keel
   • B.Wind speed, vessel's freeboard, and the angle of the wind relative to the vessel✓
   • C.The vessel's speed through the water only
   • D.Tidal current direction

   Why: Leeway is primarily determined by wind speed, the vessel's freeboard (amount of hull above water presenting wind resistance), and the relative angle of the wind. Higher freeboard and beam winds produce the greatest leeway.

10. 10. In a current triangle, what does 'drift' refer to?

    • A.The direction the current flows relative to true north
    • B.The angular difference between heading and course made good
    • C.The speed of the current expressed in knots✓
    • D.The lateral displacement caused by wind and current combined

    Why: Drift is the speed of the current expressed in knots. Together with set (direction), drift fully describes a current vector used in current triangle construction.

11. 11. The drift of a current is 2 knots and acts for 3 hours. What is the displacement vector used in the current triangle?

    • A.2 nautical miles in the direction of set
    • B.3 nautical miles in the direction of set
    • C.6 nautical miles in the direction of set✓
    • D.5 nautical miles in the direction of set

    Why: Distance equals speed multiplied by time: 2 knots × 3 hours = 6 nautical miles. The current vector plotted in the triangle has a length of 6 miles in the direction of the set.

12. 12. In a current triangle problem where the desired CMG and STW are known but the current is unknown, which two positions are needed to determine the current vector?

    • A.The compass heading and the chart magnetic variation
    • B.The dead reckoning position and the observed (fix) position for the same time✓
    • C.The departure sounding and the arrival sounding
    • D.The charted current arrow and the tidal prediction table entry

    Why: The current vector is derived from the difference between the DR position (where the vessel would be without current) and the actual observed fix for the same time. The vector drawn from DR to fix gives the set and drift of the current.

13. 13. A vessel steers 090°T at 8 knots STW into a head current setting 270°T at 3 knots. What is the SMG?

    • A.11 knots
    • B.8 knots
    • C.5 knots✓
    • D.3 knots

    Why: A head current (set 270°T, opposing eastward heading 090°T) directly subtracts from the vessel's STW. SMG = 8 − 3 = 5 knots. The CMG remains 090°T since there is no lateral deflection.

14. 14. A running fix is necessary when:

    • A.Only one charted object is visible and two bearings must be taken at different times✓
    • B.The vessel is traveling at high speed and all bearings are taken simultaneously
    • C.Three objects are visible but only two bearings can be measured accurately
    • D.GPS fails and the vessel must use only depth soundings

    Why: A running fix is used when only one charted object is available; the navigator takes an initial bearing, then a second bearing after a known run, and advances the first LOP along the course line by the distance traveled to obtain an intersection.

15. 15. A vessel is on course 180°T at 10 knots. A bearing of 090°T is taken on a radio tower at 1200. At 1300 the same tower bears 045°T. What is the label applied to the advanced 1200 LOP when plotting the running fix?

    • A.1200–1300✓
    • B.1200 ADV
    • C.1300 DR
    • D.EP 1300

    Why: The standard labeling convention for an advanced LOP is to show both the time of the original observation and the time to which it was advanced, written as 'original time–advanced time' (e.g., 1200–1300), so the navigator knows both the source time and when the running fix was obtained.

16. 16. For the most reliable cross bearing fix, the charted objects selected should have bearings that differ by approximately:

    • A.90°, or at minimum 60°✓
    • B.30°, for maximum LOP sensitivity
    • C.180°, so the objects are on opposite sides of the vessel
    • D.Any angle because bearing accuracy is independent of object geometry

    Why: LOPs cutting at approximately 90° (or within the range 60°–120°) provide the most accurate fix; angles less than 30° or greater than 150° create elongated cocked hats where small bearing errors cause large position shifts.

17. 17. When a navigator plots a fix from simultaneous cross bearings, the fix is marked on the chart with which symbol and label?

    • A.A circle with a dot at its center and the time of the fix written alongside✓
    • B.A small triangle with the word 'FIX' written inside
    • C.A half-circle with the time written alongside
    • D.An X with the letters 'EP' and the time written alongside

    Why: Per Bowditch (American Practical Navigator) and NGA Chart No. 1 plotting conventions, a fix obtained from simultaneous observations such as cross bearings is plotted as a dot enclosed in a circle with the time written alongside. A semicircle (half-circle) around a dot marks a DR position, a square around a dot marks an estimated position (EP), and a running fix is a circle around a dot labeled 'R Fix' with the time.

18. 18. A vessel is on course 000°T. A lighthouse bears 315°T (45° on the port bow). Later, the same lighthouse bears 270°T (abeam to port). This technique is known as the:

    • A.Four-point bearing (or bow-and-beam bearing)✓
    • B.Running fix by doubling the angle on the bow
    • C.Danger angle method
    • D.Horizontal danger angle

    Why: The four-point bearing method (also called the bow-and-beam bearing) involves taking a bearing when the object is 45° off the bow (four points), then again when abeam. The distance run between the bearings equals the distance off when abeam, giving a simple and reliable position estimate.

19. 19. To construct a clearing bearing on a chart, the navigator should:

    • A.Draw a line from a charted lighthouse that is tangent to the safety circle (or hazard boundary), then measure the bearing of that line from the lighthouse✓
    • B.Draw a line from the vessel's DR position to the nearest known hazard and note the bearing
    • C.Plot the reciprocal of the course line through each waypoint
    • D.Use the depth contour nearest the hazard as the clearing line

    Why: A clearing bearing is constructed by drawing a line from the charted navigation aid that just clears the hazard (tangent to a safety margin around it). The bearing of that line, measured from the navigation aid, gives the NLT or NMT value the navigator monitors during passage.

20. 20. When plotting waypoints during voyage planning, USCG and IMO guidance requires that each course line be checked to ensure:

    • A.The track clears all charted dangers by a prudent margin and that no intermediate hazard lies between waypoints that the vessel could stand into undetected✓
    • B.The track is aligned with the direction of the prevailing current to maximize speed
    • C.Each waypoint is at least 1.0 NM from the previous waypoint
    • D.The track passes within radar range of at least one fixed navigation aid

    Why: IMO Resolution A.893(21) on voyage planning requires that each leg be examined for hazards lying on or near the track, with appropriate clearing bearings, danger angles, or no-go zones identified. It is insufficient to plot just start and end waypoints without checking the full track between them.

Frequently asked questions

Is Chart Plotting on the MMC Upgrade exam?

Yes — Chart Plotting is one of the tested modules on the MMC Upgrade licensing exam. Candidates must score 70% on each module to pass.

How many Chart Plotting questions are on the MMC Upgrade exam?

The USCG draws from a bank of 154 Chart Plotting questions across all exams. The exact number on any single sitting varies, but Rules of the Road is typically the largest module and has the highest passing threshold (90%).

What is the best way to study Chart Plotting for the MMC Upgrade exam?

Work through the practice questions in this bank until you can answer them consistently above the passing threshold. Review every explanation — understanding why the wrong answers are wrong matters more than memorizing facts.