Use of deviation on running fixes

[Pelagic]

So can we now move on to the Coriolis Effect in ship Navigation?

This was one of my favorite exam questions for its effects on tanker navigation


This made me laugh.

https://www.quora.com/Does-the-corio...nchor-of-ships

[Blue Stocking]

Originally Posted by Don C L

ok, well, if no one else will say it,

True Virgins Make Dull Companions:
T + V = M + D = C
true + variation = magnetic + deviation = compass

This ^^ -- and East is least, West is best, are 2 of the first rules you learn in RYA courses.

[jackdale]

Originally Posted by capt jgw

When I'm teaching for the USCG Aux we're not allowed to use the virgins and whiskey saying, but in my Captains course, and it's all guys, I do.

Correcting - Can Dead Men Vote Twice at Elections (Bowditch uses this)

Uncorrecting - True Virgins Make Dull Company at Weddings / TeleVision Makes Dull Children

[davefromoregon]

I have forgotten where I saw it, but I enjoyed the completion of the "true virgins" version which was "add whiskey subtract ethics"

[davefromoregon]

Due primarily to poor study or insufficient practice, the test didn't go very well. The instructor who evaluated my test, seemed to think my problem involved the use of the Tursi rather than the Pyzel text.

I did find that I needed to go out to websites and YouTube for help for set/drift related problems.

So, was the problem like likely insufficient practice or is the choice of texts really the problem?

I did fine on the symbol/aton and the tide parts of the test.

[Don C L]

Originally Posted by davefromoregon

Due primarily to poor study or insufficient practice, the test didn't go very well. The instructor who evaluated my test, seemed to think my problem involved the use of the Tursi rather than the Pyzel text.

I did find that I needed to go out to websites and YouTube for help for set/drift related problems.

So, was the problem like likely insufficient practice or is the choice of texts really the problem?

I did fine on the symbol/aton and the tide parts of the test.

Is that Mike Pyzel? Did he write a text? Wow, yeah, use his.

[jackdale]

Originally Posted by davefromoregon

Due primarily to poor study or insufficient practice, the test didn't go very well. The instructor who evaluated my test, seemed to think my problem involved the use of the Tursi rather than the Pyzel text.

I did find that I needed to go out to websites and YouTube for help for set/drift related problems.

So, was the problem like likely insufficient practice or is the choice of texts really the problem?

I did fine on the symbol/aton and the tide parts of the test.

Navigation is navigation it should not matter what manual you use.

I should have sent you this link earlier. It is my PowerPoint notes for my CYA / Sail Canada coastal navigation course.

https://www.slideshare.net/JackDale/...tal-navigation

Feel free to browse through it and use anything else on the site that you choose

[Hoofsmit]

Hi Dave
Practice, practice Practice and don't give up!

For me the phase ' use it or loose it ' is very true.

I am not very good at learning, but when I have to apply new theoretical subjects in real situations it sticks - it become a skill which is then easier to recall or revise

Cts is one of these for exam questions, I find abbreviating the process to a check list to ensure my order of working and to ensure I haven't missed anything is the only way I find success , I have a page in the back of my log for this purpose

Also when at sea it is so much more practical and applied so that you realise plotting a Ep is as much a gut feeling as getting the perfect position, ( leeway varies so much in a high sea state and variable wind) the reality is that your plan of arriving at your destination at the time you have inter/ extrapolated that tidal height or steam is always a bit off.

I was told by a very respected old timer
" worry about where you shouldn't be- not where you are"

Keep trying and it will come





Sent from my iPad.......i apologise for the auto corrects !!!

[belizesailor]

Apologizies if this has already been addresed, but...

If you use the ship's compass to shoot a bearing, which you can do with a full sized binnacle mounted compass...like a nice big Ritchie Navigator...then you apply deviation per ship's heading to the bearing (as suggested...check terminology).

For example, you are sailing on a heading of 180° PSC (Per Ship's Compass or in some sources Per Steering Compass) and you shoot a bearing on an object at 090° PSC then you look up the deviation (you all have deviation cards aboard right?) for the heading of 180° PSC and apply that deviation to your bearing of 090° PSC. You then use the result for that bearing.

Somewhat of an academic exercise, since in practice it is easier and more accurate to use a hand bearing compass. It is assumed that when using a hand bearing compass that you position yourself somewhere well away from anything that would produce significant deviation...like ahead of the mast...this is also a good spot because you can steady yourself on the mast...or just sit down there if feasible. So, deviation is not applied if using a hand bearing compass.

Note that this is not specific to running fixes, but applicable any time you shoot a bearing using the ship's compass.

[belizesailor]

My recommendations for ASA 105 preparation:

https://www.dropbox.com/s/fg1vk85bcp...tions.pdf?dl=0

[belizesailor]

Originally Posted by Don C L

Is that Mike Pyzel? Did he write a text? Wow, yeah, use his.

ASA uses either the Tursi or the Pyzel text. Some prefer one over the other. Traditional coastal piloting techniques haven't changed in 100 years so its really just a matter of presentation. My preference is the Tursi text, but best to use whichever one works for you.

[jackdale]

Originally Posted by belizesailor

Apologizies if this has already been addresed, but...

If you use the ship's compass to shoot a bearing, which you can do with a full sized binnacle mounted compass...like a nice big Ritchie Navigator...then you apply deviation per ship's heading to the bearing (as suggested...check terminology).

If you use a ship's compass to take a bearing, you can and should use the deviation table. One version of a running fix, the bow and beam, uses 45 and 90 degree relative bearings. The distance run is equal to the distance off.

I have seen about three deviation tables on 50 or so boats I have sailed. My favourite was on a Bavaria 40 with speakers mounted in the binnacle. The compass adjuster had written "You have got to be kidding!"

[Lodesman]

Originally Posted by jackdale

One version of a running fix, the bow and beam, uses 45 and 90 degree relative bearings. The distance run is equal to the distance off.

That's called "doubling the angle on the bow" and is not limited to 45/90º.

[StuM]

Originally Posted by Lodesman

That's called "doubling the angle on the bow" and is not limited to 45/90º.

While one is indeed a variation of the other, they are generally regarded as two different techniques and have traditionally been given two different names.

What Jackdale calls the "bow and beam" is commonly known as the "four point bearing fix" ( i.e. four points off the bow = 45%) is intended specifically to get distance off a point when you come abeam of it.

"Doubling the angle on the bow" is a more general application of the principle underlying the "four point" technique and can be used at any stage before or after passing a point. It gives you the "distance off the shore on the second bearing".

Note: for both of these techniques, the relative bearing should actually be from the boat's course, not heading

[jackdale]

Originally Posted by StuM

While one is indeed a variation of the other, they are generally regarded as two different techniques and have traditionally been given two different names.

What Jackdale calls the "bow and beam" is commonly known as the "four point bearing fix" ( i.e. four points off the bow = 45%) is intended specifically to get distance off a point when you come abeam of it.

"Doubling the angle on the bow" is a more general application of the principle underlying the "four point" technique and can be used at any stage before or after passing a point. It gives you the "distance off the shore on the second bearing".

Note: for both of these techniques, the relative bearing should actually be from the boat's course, not heading

Bowditch (Amercian Practical Navigator) and Chapman Piloting call it a bow and beam. I am not familiar with "four point bearing fix".

Yes, it is a special case of of doubling the angle on the bow.