Chart Plot Fails

I just got done testing at the REC for 3rd Mate Unlimited NC. I passed 5/6 tests. I’ve failed the chart plot twice, even after taking Terrestrial Nav at MPT and passing the chart plot with no problem at all. The test is bullshit as far as I’m concerned. I’ve worked on boats for 15 years and I’ve never seen anyone pull out a luminous range diagram. I’ve also worked with plenty of totally incompetent mates who have passed that test. It doesn’t evaluate competence as a Mariner.

Anyway, I’m going to spend a couple weeks studying before retesting. But just wondering if there’s anyone out there in a similar situation.

-My first test was Block Island, my second Long Island, can I expect Chesapeake Bay for my next test, or is it random what chart they assign?

-Is it worth requesting the old test? What are the requirements for that?

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If you think that’s bad, try solving three star running fixes, Or determining sailing drafts or your righting moment or any other 15-30 minutes of working out a problem just to prove to them that you can.

My advice with chart plotting is read the chart, read the question thoroughly, practice and use a very fine tip mechanical pencil and a yard stick.

As far as luminous range goes, those are like gimme questions and you can learn those and get proficient with them in no time if you try.

In nominal visibility you can just use the mathematical method, square root of the height of eye, multiplied by 1.1 and that will tell you the distance of that object to the visible horizon, then do the other object and that’s the distance that you should see the object/vessel on the horizon, or at least it will get you close enough.
If the visibility is reduced just use the luminous range scale which you have access to iirc.

Not sure about the new tests, I have heard the older tests are harder but that’s just hear-say.

Also, passing the tests is not proof of competence and just proves that you were able to get the paper. Proving that you’re competent will come later.
You’re in a good situation where you have just one module to pass, which means you have just one module to study and focus on.
I would study my ass off for the rest of the time I have doing 3 chart plots per day, each of the possible charts and I’d use Lapware to generate template tests.

Good luck.

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It’s not supposed to be random. On re-takes you should be given a different chart. But, it may not always be done. This is for all re-takes, not just chart plots. You are not supposed to get the same module a second time.

If you ask, they will likely make sure you get a different module. If you don’t, you might get lucky.

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I’ve never flunked a chart plot, but I’ve had trouble with some of the practice tests.

The biggest thing is you must plot very carefully and accurately , much more carefully than you would ever do in real life.

You should be very familiar with all three charts.

Know the luminous range diagram. No big deal.

Go through the all of the question bank, its not that many questions, and do the questions that don’t require plotting. No need to waste time looking for obscure things that can be hard to find on the chart. Know where to look.

On the exam answer the questions that don’t require plotting first. Get those easy questions out of the way. They should be easy. Then do the plotting

On the plotting questions there will often be two answers that are very close. So, thats why you must be super accurate plotting.

I always did the plots twice and where I could confirmed the plot using different methods.

A good three arm protractor helps.


When I was studying for my exam I found this guy’s material to be very helpful:

He also did a video on the “new” chart plots:

He’s on here too, if you’re willing to search for him. I found $100 a small price to pay to pass the chart plot.


They changed the battery of questions recently and to make a long story short, the majority of mariners taking the tests containing the new battery failed. I studied the old battery very hard and when I took plotting I didn’t recognize a single question.

I passed it the second time around. My advice is to study using Lapware and don’t give up. You can actually corrsspond with Lapware and see if they have access to the new questions.

This would have made it a lot easier. Lol!

Did you feel they lapware more closely resembled the actual test?

Only watched a bit but that seems like a very good video. The approach used in the video uses the same as the way I learned in the CG.

Makes sense…

There’s more than one way to skin a cat of course. One way is as mentioned to be familiar with all three test charts and do all the practice problems. Another way is to use an approach that can be used with any chart and will catch errors.

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Yeah. I’ve also found that being a decent navigator makes these chart plots fairly doable. :wink:

But seriously. We have all passed these tests. They require very deliberate plotting with near zero mistakes. Some of the questions piggy back off the others, so if you screw up the first question, the second one is likely to be wrong.
Personally, I have rarely gotten the answer exactly as it is on the multiple choice option with these chart plots. Get close enough to the right answer and that is usually the one. I have also never failed one and I’ve taken 3 in my career.

Something that always helped me when it came to license equations is that you should round out to the fourth decimal place (.0000) or ten thousandth. If you do that with all your equations, you generally get the right answer. I’m not sure if that holds true anymore, but it worked for me.

Being concerned about the luminous range diagram is a bit questionable though. Those are gimme questions like the 7/10’s rule. Keep studying and it will click. Most of it is of no use in the actual world, but you can say that for a lot of stuff in life.


I’ve probably done chart plots a dozen times and never failed an USCG exam, but I certainly have had trouble with some of the practice tests.

In real life I use a rolling plotter for chart work and I have also found that to also be very good on maneuvering board and pilotage chart sketches.

However, the rolling plotter is not accurate enough for the chart plot exam, use triangles. Its also to easy to slip a bit with parallel rules, use triangles. Triangles are the most accurate plotting tool.

Some of the chart plots have (or had) a fix with three land bearings. A three arm protractor will plot that most accurately. If your plot has not arrived at that exact point, then you know that you have a previous mistake or your plotting is not precise enough.

If there is a question that asks for the depth at a certain point in the plot, obviously your plotted point must arrive closest to a spot with that depth on the chart.

There are two primary methods of plotting the set and drift problems. Know them both. These just take practice and care. Use one method to check the other.

Most errors will be set and drift, or imprecise plotting.

I found it frustrating and time consuming on the exam trying to find certain places or aids to navigation on the chart. Aids can be looked up in the light list. Named places may be found in the Coast Pilot. You need to study the charts and use the practice questions enough so that you know where these places are on the chart without having to waste time hunting for them during the exam.

Likewise there may be questions about the Notes on the charts, or the type of tides or chart datum. Know these things, and know where to find them on the chart.


I bought his material for some issues within tnav and cnav when i took the classes elsewhere. He has a way of explaining things that just seem to click. Also recently took my 200 upgrade with him using his study materials and tested through him, was very pleased. Chris has so much to offer. Awesome guy.


Things have changed and I concede that questions on the luminous range of lights are not related to the real world.
Changing nautical education to reflect changes to practice always lagged.
Navigation with aids to navigation limited to an echo sounder, magnetic compass and a radio direction receiver together with a sextant demanded a different range of skills. The luminous range of lights expected was always calculated as running on DR after days of cloudy weather we used every thing we had.
On joining a fleet run by an oil company meant that we were exposed to ARPA and an IBM integrated navigation system before the industry caught up. The manuals that came with the equipment were studied religiously. The first ARPA I used required entering the bootstrap program by entering code in hexadecimal by buttons before loading the program by paper tape.
It was some years latter I had to attend an ARPA course.
As I remember the chart work exam many years ago, the chart was not known in advance. It was the English Channel with complex tides, vertical sextant angles, fog and many other hidden problems that had to be considered. I managed to slip through along with one other, who amazingly managed to do one question twice. It had absolutely nothing to do with real life and had more in common with a qualification in technical drawing.

The problem I have with the luminous range problems is that in many of the practice problems, the range that the USCG decides is the right one doesn’t have a rational basis. I’ve seen examples problems where the USCG "right"answer is way off from what it should be. If the answers are far enough apart, you can get the right answer, but sometimes the possible answers are pretty close and you’re flipping a coin to get their answer. A person’s license shouldn’t be based on that.

The reason to be very familiar with the test charts and do the practice problems is it makes finding landmarks and aids to navigation faster. It’s not to memorize the test, but just be faster at using the chart because you know it.

I was making an observation based on watching a few seconds of the video.

The approach that tugsailor posted, that of solving or checking the plot problems a different way when possible is mentioned as is the related fact that the pubs can be used to find aids.

I think that’s a good feature of the video. YMMV.

Practice more, When I tested for C/M, I went to the USCG website they have some previous test examples there. Plotting is plotting so you can use that for practice.

The exam likely uses the procedure in Bowditch chapter 4.

Nominal, luminous and geographic ranges are explained.



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