shipping routes

[Richard10002]

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When working close to land you can get a very good idea by drawing great circles (NOT straight lines) between TSSs e.g. Ushant/Finisterre.

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Pretty sure the big ships rarely use great circles, particularly between points as close to each other as Ushant and Finisterre. I can only recall using a GC once while crossing the Atlantic from Panama to the Channel, and this took us close to Bermuda, and far enough North to enter some iffy weather patterns which resulted in one of the anchors snapping.

Given the arbitrary nature of the answer, rhumb lines between 2 points are the best answer.

 

[Refueler]

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When working close to land you can get a very good idea by drawing great circles (NOT straight lines) between TSSs e.g. Ushant/Finisterre. A gnomonic chart will help you to do that. If you want to know how close you are to one of these lines, put the start and end points of the line into your GPS and look at the XTE.

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Basic Chart work - Gnomonic charts and GC ... but why would you want to do it ? From Ushant to Finisterre especially ? If you said ushant to Ambrose Light - that's more practical.
The more you approach North - South routeing - the less need for GC as following a longitude meridian is a GC.

 

[Gunfleet]

Still, 25.50N 77.00W looks like a place to avoid according to that American routing chart!

 

[Refueler]

I'll look later ..

 

[Refueler]

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Still, 25.50N 77.00W looks like a place to avoid according to that American routing chart!

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25 50.00 N or 25.5 N and 77W - not having a Pilot Chart in front of me ... one corresponds to approach to Hole in the Wall, South Bahamas ... other to within Providence Channel.

Without calling up Pilot Charts ... what did you find they reckoned ?

In that region of course - many ships if proceeding north would take the inner route up US coast to gain the Gulf Stream and local currents that run strong. Exiting north of Bahamas.

 

[Mariner69]

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I applaud the replies that give links to Pilot Charts etc. But in reality - they are rarely followed.

There are enough ships persons on these forums and I'm surprised by lack of response from them. Even if they were to post and disagree with me ! (I'd hope they would give reason for my being wrong !)

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I would suggest that for the yachtsman sailing across the ocens that the auxillary powered directions in the Ocean Passages for the World (NP 36) would be useful. This way they are unlikely to meet many commercial vessels.

The fact that commercial vessels will use rhumb lines for some tracks and GC for others will be dictated by the charterers.

On a slow old Clan ship in the 70's I used the auxillary routes as a hint. On faster bulk carriers we were obliged to go via the shortest GC route even though that took us up in towards the ice whereas I much prefered the composite rhumb line down the channel to the horse latitudes then straight across. This way we could do a lot of maintenance in good painting weather.

Horses for courses so to speak /forums/images/graemlins/smile.gif

 

[Gunfleet]

I just idly looked at the US routeing charts link posted in this thread and realised that position was the convergence of cross atlantic and local shipping routes, national boundaries, strong currents, sandbanks and the occasional tropical storm/hurricane. Then a guy is a 25ft sailing boat crosses your bows! As others have said, thanks for the pictures, they do make the point in a very telling way.

ps slow reply owing to laptop nightmare. Bloody computers.

 

[Refueler]

[ QUOTE ]
I just idly looked at the US routeing charts link posted in this thread and realised that position was the convergence of cross atlantic and local shipping routes, national boundaries, strong currents, sandbanks and the occasional tropical storm/hurricane. Then a guy is a 25ft sailing boat crosses your bows! As others have said, thanks for the pictures, they do make the point in a very telling way.

ps slow reply owing to laptop nightmare. Bloody computers.

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I know from my own experience that region has strong currents that are not to be looked on lightly. It is also a Hurricane / Tropical Storm Corridor that needs careful watching.