Question for any instructor/examiner?

[alexincornwall]

In fact, if the 3 lines do cross exactly, there is more chance that they are wrong than right..

I think I once read somewhere that, despite most of us putting a dot in the middle of the cocked hat, in order to mark our position, there is a strong chance that the actual position is outside the cocked hat. It was a long time ago, so I cant recall how it was justified, but I recall it being a well made point.

The ‘dot’ should ideally be placed in what would be perceived as the most dangerous part of the triangle so that a plot can be worked away from that point.

 

[Babylon]

The ‘dot’ should ideally be placed in what would be perceived as the most dangerous part of the triangle so that a plot can be worked away from that point.

Just what I was going to say!

Re the OP's wife, if she knows the rest of the stuff (she certainly sounds diligent and keen to succeed) and the instructor fails her for insufficient nano-accuracy on this one item, then I suggest she asks for the paper to be referred to the RYA.

 

[Paulfireblade]

Hi,
I am currently doing my Day Skipper Shorebased RYA Theory with Navathome online course which is pretty rigid as can be expected with an online course even to the point that they find some practices suggested in RYA handbook as not sufficient, but even they accept a “cocked hat” and suggest as @alexincornwall mentions to assume you are within the cocked nearest to any nearby danger.

I wish her success.

 

[scotty123]

Hi,
I am currently doing my Day Skipper Shorebased RYA Theory with Navathome online course which is pretty rigid as can be expected with an online course even to the point that they find some practices suggested in RYA handbook as not sufficient, but even they accept a “cocked hat” and suggest as @alexincornwall mentions to assume you are within the cocked nearest to any nearby danger.

I wish her success.

The RYA courses, have always taught that your assumed position if a cocked hat, is nearest to the hazard, it isn't a novel concept.
PS, the RYA handbook, if read properly, explains everything, no additional books are needed, however some people think their 'cartoon' format is somehow beneath them.

 

[lw395]

The RYA courses, have always taught that your assumed position if a cocked hat, is nearest to the hazard, it isn't a novel concept.
PS, the RYA handbook, if read properly, explains everything, no additional books are needed, however some people think their 'cartoon' format is somehow beneath them.

The idea that the corner closest to 'the hazard' gives any hard limit to your position is plain wrong.

 

[Baddox]

Does such a fail have any consequences other than to pride?

The theory is a base to be used in real life or to help in the DS practical that leads to a qualification that can be used for charter rental.

First mate is about to do her DS theory. Her instructor has told her that any innaccuracy in plotting a fix will lead to fail. in revising ahead of tomorrow's exam, she has just obtained a 100 yard "cocked hat" and is now convinced she will fail.

I am trying to say that a 100 yard margin of error (from an object 3.5m away) is acceptable. It's a fraction of a degree, the thickness of the lines on the plotter. A big cocked hat is a prompt that you made a significant plotting error, then you check again.

More importantly in real world, if visibility is such that you can see 3.5 miles, 100 yards in open water (which you've covered several times over in the time taken between fixes) is simply neither here nor there. If you are within 100 yards of an unmarked hazard and you don't know it's there or which way lies safe water, a far-off fix isn't much good to you.

Am I right? Or is the instructor right to indicate that all 3 lines must actually cross? Trying to help 1st mate through something she is finding quite tough.

 

[scotty123]

The idea that the corner closest to 'the hazard' gives any hard limit to your position is plain wrong.

Really, why?

 

[LadyInBed]

How big is the boat? 100 yds when on a tanker isn't a lot!

 

[Uricanejack]

Really, why?

I wouldn’t call it plain wrong, it is kind of wrong.

Ussing the closest cross to the danger is just an assumption. your error might be the closest point to the danger. Or completely different even the furthest.Logic if used is worse case so the unknown error puts you further away from danger rather than close.
bottom line it’s still just an assumption.
Your true position could still be closer to the danger than you believe.

Its a reasonable assumption, which probably puts your error on the side of safety.

There is a whole mathematical probability method which made my head hurt. I always thought it was still just a fancy way of guessing which of your position lines are more likely to have an error.
So backto a reasonable assumption

 

[Richard10002]

When we take a series of position plots, it creates our track on the chart, or at least the trend of our track. It will normally be obvious what the most likely track has been, and whether a particular plot was in error. If concerned, you should increase the frequency of the plots. It's rare that you don't have time to take a series of plots but, if worried that you are actually in danger, and have no time, you should alter course in such a way that is most likely to take you away from the danger.

Doesn't help the OP, because we are talking about a single plot, and it has already been said that, in a test situation, and unlikely as it might be in real life, it could be designed so the bearings cross at a single point, provided any corrections have been applied correctly.

 

[Paulfireblade]

PS, the RYA handbook, if read properly, explains everything, no additional books are needed, however some people think their 'cartoon' format is somehow beneath them.

I Think the RYA Handbook is excellent and have read it from cover to cover and was surprised when I quoted advice given in it as an answer in my online Coursework and it was marked as wrong. When I questioned it I was quoted collision regs and they suggested although it was a method they did not consider it safe enough so all I am saying is that if they are that strict but consider a “cocked hat” acceptable then the Person referred to in the OP should be okay.

 

[scotty123]

I wouldn’t call it plain wrong, it is kind of wrong.

Ussing the closest cross to the danger is just an assumption. your error might be the closest point to the danger. Or completely different even the furthest.Logic if used is worse case so the unknown error puts you further away from danger rather than close.
bottom line it’s still just an assumption.
Your true position could still be closer to the danger than you believe.

Its a reasonable assumption, which probably puts your error on the side of safety.

There is a whole mathematical probability method which made my head hurt. I always thought it was still just a fancy way of guessing which of your position lines are more likely to have an error.
So backto a reasonable assumption

So if you assume you are closer to the danger, than the cocked hat assumes you are, what do you do?
Exactly the same thing, you avoid the danger by sailing away from it.
It isn't mathematics, its common sense.
If you were blindfolded & placed near the cliff edge at Beachy Head, would it matter if you didn't know exactly how close to the edge you were?
Of course not, no-one with any sense would walk toward it, the distance, regardless of accuracy is academic, you get away from the danger until you are safe, then reassess.

 

[shaunksb]

If you were blindfolded & placed near the cliff edge at Beachy Head, would it matter if you didn't know exactly how close to the edge you were?
Of course not, no-one with any sense would walk toward it, the distance, regardless of accuracy is academic, you get away from the danger until you are safe, then reassess.

Surely it would Alant or you’d walk across the nearby road and get run over.

_______________________

 

[lw395]

So if you assume you are closer to the danger, than the cocked hat assumes you are, what do you do?
Exactly the same thing, you avoid the danger by sailing away from it.
It isn't mathematics, its common sense.
If you were blindfolded & placed near the cliff edge at Beachy Head, would it matter if you didn't know exactly how close to the edge you were?
Of course not, no-one with any sense would walk toward it, the distance, regardless of accuracy is academic, you get away from the danger until you are safe, then reassess.

That's a simplistic answer.
With added ridiculous example.
What are you going to do, sailing along the South Coast? Keep sailing South, away from 'the danger'?
Sometimes you need to know where you are, to a reasonable accuracy, and have some grip on what that accuracy is.

 

[Spirit (of Glenans)]

It's a THEORY TEST. The bearings are not taken by the candidate, they are GIVEN on the paper, and if plotted correctly on the Training Chart, will always result in a reasonable-sized cocked hat. The only time they can result in a tiny one, or an exact position, is when Variation and Deviation have been applied incorrectly.
I've been there and done that, and have had the error explained to me by the instructor!

 

[lw395]

It's a THEORY TEST. The bearings are not taken by the candidate, they are GIVEN on the paper, and if plotted correctly on the Training Chart, will always result in a reasonable-sized cocked hat. The only time they can result in a tiny one, or an exact position, is when Variation and Deviation have been applied incorrectly.
I've been there and done that, and have had the error explained to me by the instructor!

They presumably set the exercises so they are easy to mark and so they expose not understanding the process.
That's normal in training and education.

 

[scotty123]

Surely it would Alant or you’d walk across the nearby road and get run over.

_______________________

Stupid response.

 

[scotty123]

That's a simplistic answer.
With added ridiculous example.
What are you going to do, sailing along the South Coast? Keep sailing South, away from 'the danger'?
Sometimes you need to know where you are, to a reasonable accuracy, and have some grip on what that accuracy is.

No, sail away from the hazard, until you are at a safe distance from the danger, then re-assess situation. Surely even you will have kept a log of previous progress & have some EP, so know roughly where you are, you already have a chart, otherwise you couldn't plot your cocked hat, rather than sail to France & ask them "where am I?"
What, is ridiculous about the example, since you obviously are having difficulty with the logic?

 

[lw395]

The point of a fix, is it stands alone and doesn't depend on your DR plot.
If you start by thinking you know roughly where you are, you may get into trouble.
The question should be more 'where could I possibly be?' and 'how does this fix limit that?'.
Ask yourself how far out those bearings could possibly be.

 

[scotty123]

The point of a fix, is it stands alone and doesn't depend on your DR plot.
If you start by thinking you know roughly where you are, you may get into trouble.
The question should be more 'where could I possibly be?' and 'how does this fix limit that?'.
Ask yourself how far out those bearings could possibly be.

Like was wrong button.

A fix, like any other positioning method, does not stand alone, no one would depend upon a single input of information, but it with the other information you have, is an additional confirmation. However, your fix does indicate where any danger lurks, so if you want to ignore it, why bother taking it at all? How far out they could be, is academic, they simply tell you to clear out of danger.
Why are you arguing over a method used by mariners for centuries?