Chart Plotting USCG Exam: How to Pass Every Problem

Chart plotting is the only module on the USCG license exam that requires physical skill, not just knowledge recall. Nine problems, a real NOAA paper chart, parallel rules or a rolling plotter, dividers, and a pencil. No computer. No GPS. You are expected to navigate the way mariners did before electronics, and you need to do it accurately under time pressure.

Most candidates who struggle with chart plotting aren't weak on the concepts — they're weak on the mechanics. The fix is repetitive practice with the actual physical tools. Here's everything you need to know about what the exam tests, the specific problem types, and how to build reliable plotting skills.

The Exam Format

The chart plotting module consists of 9 plotted problems on a NOAA chart. The NMC uses a small set of standard charts for the exam — Chart 116 (Straits of Florida) and Chart 1210 (Narragansett Bay area) are among those commonly used, though the NMC can change the chart used at any center.

Passing score: 70% (roughly 7 of 9 problems correct).

You bring your own equipment or use what the testing center provides:

• Parallel rules or a rolling plotter (either is acceptable; learn one and use it consistently)
• Dividers
• Pencil and eraser
• Calculator (basic functions only — the problems don't require scientific functions)

The exam doesn't provide a compass for measuring — you read bearings off the compass rose using parallel rules. If you're not practiced at walking parallel rules across a chart, this is the skill to develop first.

Equipment: Rolling Plotter vs. Parallel Rules

Both work. The rolling plotter (also called a parallel plotter or rolling ruler) is faster for many candidates because it doesn't "slip" when moved across the chart the way parallel rules can. The parallel rules are traditional and found at every marine store.

Pick one. Practice only with that tool. A candidate who switches tools on exam day almost always makes errors.

The Seven Problem Types

The USCG chart plotting exam draws from a fixed set of problem categories. You won't see all of them in every nine-problem set, but knowing all of them prevents surprises.

1. Course and Distance

Given: starting position and destination. Find: true course and distance.

The procedure:

1. Plot both positions on the chart (lat/long given, or described by reference to a charted feature)
2. Draw a line between them
3. Walk the parallel rules to the nearest compass rose and read the true course
4. Measure the distance with dividers, walk the dividers to the latitude scale, and read nautical miles

The trap: Reading course off the compass rose in the wrong direction. If your course is roughly northeast, your answer should be between 000° and 090° (roughly). A reading of 225° would be the reciprocal. Always sanity-check your course against the cardinal direction.

2. ETA (Estimated Time of Arrival)

Given: departure position, course, speed, and departure time. Find: ETA at destination.

The formula: Distance ÷ Speed = Time elapsed. Add to departure time.

Convert time in decimal hours back to hours and minutes for the answer. Many candidates make arithmetic errors here — write the conversion out explicitly.

3. Dead Reckoning Position

Given: starting position, course, speed, and elapsed time. Find: position after the stated time.

The procedure:

1. Convert time and speed to distance: Distance = Speed × Time
2. From the starting position, draw a line in the stated true course
3. Measure out the distance along that course using dividers
4. Read the lat/long of the resulting position

4. Current/Leeway Problem

Given: course steered, speed through water, current set and drift, time elapsed. Find: position made good over ground.

The vector addition:

• Plot the DR (dead reckoning) position based on course steered and speed
• From the DR position, plot the current vector (set = direction current is flowing toward, drift = speed in knots)
• The head of the current vector is your actual position over ground

Current direction is tricky: set is the direction the current is moving TOWARD (not from). A current setting 090° moves eastward.

5. Course to Make Good Against Current

Given: intended course over ground, current set and drift, vessel speed. Find: course to steer.

This is the reverse of the current problem above — you know where you want to go, and you need to back-solve for the heading that, when added to the current vector, produces the desired track.

The diagram: from your starting position, draw the intended track. From the end of the current vector (drawn from the starting position), strike an arc with radius equal to vessel speed. Where it intersects the intended track gives you your destination arrival point. The heading from starting position to that intersection is the course to steer.

6. Distance Off by Bow and Beam Bearings

Given: a bearing to a charted object when it's 45° on the bow, a bearing when it's 90° on the bow (abeam), and vessel speed. Find: distance off when abeam, or CPA.

The math: distance run between the 45° bearing and the abeam bearing equals distance off when abeam. It's geometric (isoceles triangle) and doesn't require plotting on the chart — though knowing the principle helps with the associated current/position problems.

7. Danger Bearing and Clearing Bearing

Given: a charted danger (shoal, rock, obstruction) and a charted landmark. Find: the clearing bearing that keeps you safe from the danger.

Draw a line from the landmark that just clears the danger on its safe side. Read the bearing. This is the clearing bearing — if the bearing to the landmark stays on the safe side of this value as you proceed, you're clear of the danger.

Using the Compass Rose Correctly

Every NOAA chart has at least one compass rose — two concentric circles with degree graduations. The outer circle is true north (aligned to geographic north). The inner circle is magnetic north for the chart's location, already accounting for local magnetic variation.

For exam problems, work in true bearings. Parallel rule to the outer (true) compass rose.

When a problem gives you a compass bearing and asks you to plot it, you must first convert it to true:

1. Apply deviation (from the vessel's deviation table, if given)
2. Apply variation (from the chart's compass rose)
3. Plot the resulting true bearing

Common Errors

Misreading the compass rose. The rose has values every 10° with small marks every degree. Misreading by 5° or 10° produces wrong answers. Read carefully.

Using the wrong latitude scale for distance. On most NOAA charts, the latitude scale (side margins) is your distance scale — one minute of latitude = one nautical mile. The longitude scale (top and bottom margins) is NOT a distance scale and changes with latitude. Always measure distances on the latitude scale.

Sign errors on deviation/variation. When given a deviation table, apply deviation to the compass bearing to get magnetic, then apply variation to get true. Reversing this order produces wrong answers.

Forgetting to sanity-check direction. Before you write down any course answer, glance at the chart. Is your bearing consistent with the visual direction between the two points? A northeast-bound vessel should have a course between roughly 020° and 080°.

Practice Strategy

Buy NOAA Chart 116 or the NMC practice chart. Practice plotting problems by hand, with your actual exam equipment, on real paper charts. Digital practice doesn't transfer.

Work 50+ problems before your exam. The types repeat. After enough practice, the procedure is automatic and you're not thinking about the mechanics — you're just solving the problem.

Time yourself. Nine problems in a timed session. Know how fast you need to work and build the habit of checking your answer before moving on.

Learn to read the lat/long grid precisely. Position errors cascade through every downstream calculation. Practice reading positions to the nearest 0.1 minute.

Practice with Binnacle School

Understanding chart plotting concepts is different from being able to execute them under time pressure. [Binnacle School](/school) covers the conceptual framework for every chart plotting problem type, with worked examples and the procedural steps laid out clearly so you can recognize each problem type and execute the right approach.

Sharpen your chart plotting skills at Binnacle School →

Binnacle AI is not affiliated with the U.S. Coast Guard or the NMC. Exam formats reflect current NMC guidance as of 2026 — verify at uscg.mil/nmc before sitting your exam. Not legal advice.