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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #1  
Old 02-12-2014
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ASA Coastal Nav Exam - HELP

I have been working on the ASA Instructor packet. I passed the ASA exam several years ago, and was looking forward to teaching this stuff...

For my OUPV I received 100% on the navigation skills assessment. However, the ASA Coastal Navigation Review question number 6 has me stumped.

You can find the entire ASA Coastal Navigation Examination Review Questions & Answers here

Based on Chart 1210 TR, Year 1985
Here is the relevant section of the chart;


Quote:
5) Plot a course from the W Or “A” (41° 16.6'N, 071° 24'W.) to Whale Rock buoy (41° 26.7'N, 071° 25.2'W)
a) What is the course?

Magnetic: 010º m

Compass: 015º psc

From a DR position abeam of R”2" (41° 20'N, 71° 28.6'W), plot a danger bearing to avoid the wreck east of your course line (wreck is east of buoy W Or “E”). Use Brenton Reef Light for your bearing.

b) The danger bearing is: Magnetic: 017º m

c) Brenton Reef Light should bear NO MORE/NO LESS (delete one) than the danger bearing to remain safe. NO LESS - The bearing should INCREASE as you pass the wreck.
Eazy peazy... My answers above (in RED) are within 1º of the answers on the review. But now things go astray

Quote:
6) At 1600, on the same course established in question 5, the Point Judith Light (GP Occ (1+2)) bears 300°M. At 1620, the same light bears 270°M. Both bearings are taken with a hand-bearing compass (assume no deviation). Plot a running fix for 1620. Boat Speed is 4 knots.
Let me plot this;



20 min at 4 knots = 1.333 knots

Quote:
a) What is your Running fix position? Lat: 41º 22.5' N Long: 71º 24.65' W
The lattitude answer is OK (answer sheet says 41º 22.35') but the longitude is wrong. 71º 25.7'
Quote:
b) What is the Course Made Good/Track from the W Or “A”buoy? Magnetic:
without a valid fix, I cannot compute this, or any of the following.
Quote:
Assume the difference between the Course Made Good and the heading to be due to leeway (no
current).
c) What is the leeway?

Considering leeway, plot a new course to the Whale Rock buoy.

d) What is the course? True:

e) What is the heading? Magnetic:

Compass:
I know that a bunch of you have been down this road, and believe that I cannot be the only one to be stumped by this.

Am I missing something obvious? Careless error somewhere?

Also, because I have found all of this stuff posted elsewhere online, I don't believe that I am giving anything away. I think that it may also help others that follow in my wake...
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Last edited by eherlihy; 02-12-2014 at 11:51 AM.
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Old 02-12-2014
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Re: ASA Coastal Nav Exam - HELP

I'm at work now so I don't have my book and notes, so I can't remember if this was one of them, but....

There are a couple typos in the book we used. I took 105 a year ago and if I'm remembering correctly there were two instances where things didn't/couldn't work out.
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Re: ASA Coastal Nav Exam - HELP

I have not tried to plot this but
No deviation still mean that you must take magnetic variation into account.
Also the yearly changes..
I can see that you plotted m, I would have converted to t(rue) before plotting.
In your case
Compass = Magnetic (since no deviation)
Magnetic != true (Because magnetic variation)

And if the distance between the two positions is different from your DR position you must move your track parallel to the plotted course so your triangulation is correct.

I would be skeptic if your observed position after these two bearings is the same as your plotted (DR) position.

Sorry if I'm using different words than you are used to, I learnt to navigate in Norwegian..

Last edited by knuterikt; 02-12-2014 at 02:33 PM.
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Re: ASA Coastal Nav Exam - HELP

Quote:
Assume the difference between the Course Made Good and the heading to be due to leeway (no
current).
c) What is the leeway?

Considering leeway, plot a new course to the Whale Rock buoy.

d) What is the course? True:

e) What is the heading? Magnetic:
The follow up questions indicate that I'm on the correct track
Your plot is nor complete, you should most probably have found that you have leeway after plotting those two bearings.
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Old 02-12-2014
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Re: ASA Coastal Nav Exam - HELP

Quote:
Originally Posted by knuterikt View Post
I have not tried to plot this but
No deviation still mean that you must take magnetic variation into account.
Also the yearly changes..
I can see that you plotted m, I would have converted to t(rue) before plotting.
In your case
Compass = Magnetic (since no deviation)
Magnetic != true (Because magnetic variation)

And if the distance between the two positions is different from your calculated position you must move your track parallel to the plotted course so your triangulation is correct.

I would be skeptic if your observed position after these two bearings is the same as your plotted (DR) position.

Sorry if I'm using different words than you are used to, I learnt to navigate in Norwegian..
Thanks for the reply, but this is an academic exercise. Deviation is not requested for this question, and therefore not relevant, because it is an exercise.

Variation is already factored in to the chart (look at the compass rose). I believe that we can safely assume, because it is an exercise, that the navigator is preforming these calculations in 1985.

I think that the central issue is that I have plotted a course, and am asked to plot a running fix at 1600 and again at 1620. I don't know when I left the starting location, and I don't have a second bearing to compute a fix...

wait a min...

Because I KNOW the intended course, I could assume that I am traveling parallel (or almost parallel) to that course. I KNOW the distance that I should have traveled over 20 min = 1.333 nautical miles. I suppose that I could find a place on the running fix that corresponds to 1.3 nautical miles.

Your use of english, and navigation terms are very good.
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Re: ASA Coastal Nav Exam - HELP

Quote:
Originally Posted by eherlihy View Post
Thanks for the reply, but this is an academic exercise. Deviation is not requested for this question, and therefore not relevant, because it is an exercise.

Variation is already factored in to the chart (look at the compass rose). I believe that we can safely assume, because it is an exercise, that the navigator is preforming these calculations in 1985.

I think that the central issue is that I have plotted a course, and am asked to plot a running fix at 1600 and again at 1620. I don't know when I left the starting location, and I don't have a second bearing to compute a fix...

wait a min...

Because I KNOW the intended course, I could assume that I am traveling parallel (or almost parallel) to that course. I KNOW the distance that I should have traveled over 20 min = 1.333 nautical miles. I suppose that I could find a place on the running fix that corresponds to 1.3 nautical miles.

Your use of english, and navigation terms are very good.
I could not read the yearly change on your uploaded picture, nor did I try to plot. I was trying to analyse it from the start..

You have to find a line parallel to the plotted course where the distance between the two bearing lines is 1.333 nm
Next step is to calculate leeway, and answer the remaining questions
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Re: ASA Coastal Nav Exam - HELP

Quote:
Originally Posted by knuterikt View Post
I could not read the yearly change on your uploaded picture, nor did I try to plot. I was trying to analyse it from the start..

You have to find a line parallel to the plotted course where the distance between the two bearing lines is 1.333 nm
Next step is to calculate leeway, and answer the remaining questions
BINGO!!


This is what I surmised in Post #5... I had done this years ago, but appear to have forgotten.

Running Fix is now Lat: 41º 22.8'N Long: 71º 25.9'W
Close to the answer sheet's; 41º 22.35'N 71º 25.7'W

Course made good by my calculations is now 000ºm - answer sheet says 003ºm

This seems REALLY imprecise because I have no idea if the current or wind are helping or hurting my fix....
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Last edited by eherlihy; 02-13-2014 at 05:40 PM.
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Re: ASA Coastal Nav Exam - HELP

Looking closer, I changed CMG to 001ºm - close enuf to 003º
Here is the revised chart;


For leeway, I calculated 009º
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Last edited by eherlihy; 02-12-2014 at 03:46 PM.
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Re: ASA Coastal Nav Exam - HELP

Just a little comment on your approach to solving the exercise.

If you are going to teach navigation to students I think it is good practice to do stuff the proper way.
Always plot courses and bearings using true direction.
Always use variation and yearly change in calculations.

It's better to learn a method that works everywhere & every time instead of methods that work sometimes..

If you combine modern plotters with traditional navigation it is important to operate with one type of directions, the plotter will happily give you true bearing and COG.
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Old 02-24-2014
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Re: ASA Coastal Nav Exam - HELP

Quote:
Originally Posted by eherlihy View Post
Looking closer, I changed CMG to 001ºm - close enuf to 003º
Here is the revised chart;


For leeway, I calculated 009º
That is not how to calculate a running fix. You advance the first bearing (LOP) by the distance traveled.

60 D = ST
D= ST/60
D= 4*20/60
D=1.333 miles

Advance the 1600 bearing by 1.3 miles. Where that Advanced LOP intersects the 1620 LOP is the RFix.

These are my notes on doing a running fix

http://www3.telus.net/jackdale/navlessons/Running.pdf
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