Chart plot practice on your own paper chart
Get a fresh plotting problem, work it on your chart with dividers and parallel rules, type what you measure, and see it graded within a stated tolerance, with the worked solution and a drawing.
Practice only, not for navigation. This practice is our own. It is not affiliated with, endorsed by, or connected to the United States Coast Guard or the National Maritime Center, and it copies no exam question. How the problems are worked.
A practice area defined by latitude and longitude only. The tool knows nothing of the chart's features.
Dead reckoning, Block Island Sound
Dead reckoning, 3 legs
At 0545 your position is 41° 08.7' N, 071° 41.1' W. You steer 315° T at 10.5 knots until 0605, then 255° T at 10.5 knots until 0625, then 000° T at 10.5 knots until 0640. No current is known.
Find your 0640 DR position.
- Position at 0545
- 41° 08.7' N, 071° 41.1' W
- Leg 1, 0545 to 0605
- 315° T, 10.5 knots
- Leg 2, 0605 to 0625
- 255° T, 10.5 knots
- Leg 3, 0625 to 0640
- 000° T, 10.5 knots
- 0640 DR position: within 0.3 mile of the answer
Practice only, not for navigation. Code BIS-DR-C29HO
Worked solution
Plot it on your chart or a plotting sheet with dividers and parallel rules, type what you measure, then check. The worked steps and a drawing of the plot appear here.
Open a problem by its code
Printed under every problem, for example BIS-DR-0B7Q4. The same code always gives the same numbers.
Ten question mock
Ten problems across the five calculation types in one timed sitting, graded together at the end against a 90 percent bar, with a result sheet you can print and every worked solution.
The ten question mock is part of Premium. See what Premium adds.
What the problems are based on
Every problem is generated by this site's engine from latitude and longitude, courses, speeds, times, current, variation and deviation stated in the problem. It names no charted light, buoy, landmark or depth. Mercator sailing with meridional parts on a sphere; one nautical mile is one minute of latitude; current set is the direction the water flows toward; easterly variation and deviation are positive.
The working areas are latitude and longitude boxes we drew over open water. The tool does not know the chart's features, so a generated track is a number exercise and never a safe route.
A real chart plot module also asks for bearings of charted lights, buoys and landmarks, fixes from three bearings on charted objects, course to steer allowing for leeway as well as current, and chart reading questions (bottom type, bridge clearance, tides and the Coast Pilot). This tool covers none of those; it drills the calculation and plotting skills underneath them.
Dead reckoning, course and distance, and speed, time and distance problems are free without limit, each with its worked solution. Premium adds current, compass conversion and running fix (an extra) problems, the timed ten question mock, printable sets with answer keys and the weak-area summary.
Tolerances
- Position
- within 0.3 mile of the answer
- Course or bearing read from the chart
- within 2 degrees
- Compass conversion
- within 1 degree
- Deviation
- within 1 degree, named east or west correctly
- Set of the current
- within 5 degrees
- Distance
- within 0.2 mile
- Speed, speed made good or drift
- within 0.2 knot
- Time of day
- within 3 minutes
Rounding
- Positions to 0.1 minute of latitude and longitude
- Courses, bearings, headings and set to the whole degree
- Distances to 0.1 mile, speeds and drift to 0.1 knot
- Times on a 24 hour clock to the minute
- Deviation read between table entries to 0.1 degree
- Answers are worked from the givens as printed, and graded against the unrounded result
Working areas
Each working area is a practice area defined by latitude and longitude only. The tool knows nothing of the chart's features inside it: depths, shoals, wrecks, channels, anchorages, traffic lanes, restricted areas, lights and buoys.
- Block Island Sound: 41 08.0 N to 41 15.0 N, 071 50.0 W to 071 40.0 W, between Montauk and Block Island, on a chart of Block Island Sound such as the training edition numbered 13205 TR. Variation used: 15° W, the figure the public sample modules for 13205 TR state, given in every compass problem.
- Eastern Long Island Sound: 41 07.0 N to 41 10.0 N, 072 47.0 W to 072 32.0 W, mid sound between the two shores, on a chart of eastern Long Island Sound such as the training edition numbered 12354 TR. It is a narrow box, three miles north to south, kept more than two miles from the Falkner Island group. It crosses a cable area. Variation used: 14° W, the figure the public sample modules for 12354 TR state, given in every compass problem.
- Rhode Island Sound: 41 16.0 N to 41 22.0 N, 071 20.0 W to 071 06.0 W, south of Newport and east of Point Judith, on a chart of Martha's Vineyard to Block Island such as the training edition numbered 1210 Tr. That chart is a common teaching chart; it is not one of the three charts used in the exam room. It crosses the Buzzards Bay traffic separation scheme and overlaps an anchorage ground off Brenton Point. Variation used: 15° W, our own round figure, given in every compass problem.
- Lower Chesapeake Bay: 37 07.0 N to 37 14.0 N, 076 12.0 W to 076 04.0 W, inside the bay, north of the bridge and tunnel crossing, on a chart of the Chesapeake Bay entrance such as the training edition numbered 12221 TR. It crosses ship channels (York Spit Channel and the York River entrance channel), an anchorage and a charted wreck. Variation used: 9° W, the figure the public sample modules for 12221 TR state, given in every compass problem.
The formulas, step by step: how the chart plot problems are worked. Counting sea time for the same license? Open your sea time log or read OUPV vs Master sea time.