17-Jun-2002 -- Sailing from the Pentland Firth North of Scotland on the Great Circle Route
to the Cape Race (Southeastern tip of Newfoundland), thence to the Straits
of Florida and finally to Pascagoula MS, today we passed Sable Island, in which vicinity there is 44°N/60°W.
Sable Island lies 150 naut. miles
(280 km) ESE of
Halifax (Nova Scotia) on
Sable Island Bank, and with its adjacent shoals it is a serious hazard to
The Island is reported to moving slowly East, the action of the wind and sea
causing the sea to encroach on the West end and the land to extend at the
Sable Island consists of a narrow crescent of sand about
37 km long and less
than 1,8 km wide formed by two nearly parallel sand ridges which terminate
at their West end in West Spit, and at their East end in East Spit.
The ridges are shaped by winds into hills which frequently change their
position, Many of these hills terminate in steep cliffs while others are
covered with grass behind broad sandy beaches.
There are shrubs but no trees.
The South Ridge seldom rises to a height of more then 4-6 metres, but the
North Ridge attains heights of up to 24 metres.
The island is generally featureless apart from East and West End
Further there are buildings of a meteorological station and several radio
masts near West Spit.
The most prominent radar target is the tower of West End Lighthouse.
The Canadian Wild Life Service and the Department of Fisheries and Oceans
have stations located about 1 km SE of East Spit. These are inhabited for
about 6 months of the year.
The Canadian Atmospheric Environment Service maintains a meteorological
station near West End Lihthouse which is manned throughout the year.
A herd of wild ponies exists on the island, sustained by the sparse
Sable Island is administered by the Government of Canada. Except for
emergencies no person is allowed to land, visit or reside on the island
without permission of the District Manager of the Canadian Coastguard
(residing at Dartmouth, Nova Scotia).
Above we mentioned the word "Great Circle".
What is Great Circle Sailing?
First of all we have to remember that Earth is a sphere.
Shortly spoken, a ship (or an airplane) has two possibilities to perform a
On short distances, when sailing along the coast from cape to cape, in
restricted waters or in traffic separation schemes, "straight" courses are
maintained. Such courses appear on the map as straight lines. This is the so
called "Rhumb Line Sailing".
But rhumb line sailing has a disadvantage:
A course on a rhumb line is NOT the shortest connection between two points!
Whenever feasible, however, especially on long open ocean passages in
preferably East-West-directions, the navigator will choose to sail on a
Feasibility depends mostly on meteoroloical circumstances.
A Great Circle is a circle whose plain intersects with the centre of the
Earth. So we know already two kinds of natural Great Circles:
1- the Equator
2- all Meridians, and so we understand that when sailing on North-South
directions, a Great Circle is not necessary to be calculated, as you anyway
follow it, when sailing along a meridian.
Sailing on such a line means automatically to sail on the shortest distance
between two points.
Through any two points on the Earth a Great Circle can be put. This requires
a basic knowledge of spheric trigonometry. Triangles on a plain area differ
from those on a sphere. The sum of the three angles in a plain triangle is
always 180°, a spheric triangle, however, can have more then 180°.
It would not take us anywhere to develop the necessary formulas here, a
mathematician called Napier did it already for us, many centuries ago.
On a map a Great Circle (G.C.) appears as a poleward
bended line. It is no longer a straight Rhumb Line (R.L.), but a kind of
arch consisting of many different courses, to be altered at e.g. every 5° of
longitude accordingly. And now we do understand why it is not always
feasible to sail on it. Often the Great Circle brings you too much North
into bad weather.
The selection of the best track for a passage demands skilled evaluation of a
number of factors, the principal of which or the sea conditions, winds and
currents which it is expected to encounter, and the way the ship herself
will react to them.
The North part of the Atlantic Ocean experiences predominantly unsettled
weather on the Northern side of the oceanic anticycloons (High pressures).
As a result of the almost continuous passage of depressions across this zone
the wind varies greatly in direction and strength, and there is a high
frequency of strong winds.
Gales are common. The stormiest belt extends roughly from the vicinity of
Newfoundland to the channel between Iceland and Scotland.
The central and East sections of this belt are especially stormy and strong
winds may be expected throughout the year.
This time, however, we could perform a perfect Great Circle. Lets calculate
how much time and fuel we saved with it:
Departure point: Pentland Firth (Scotland) 58°45'N / 3°10'W
Arrival point: Cape Race (Newfoundland) 46°35'N / 53°00'W
Rhumb Line distance:
only one course (248°)
1945 nautical miles
Great Circle Distance:
initial course 269°, then gradually turning down to arrival course 224°)
1901 nautical miles
Difference: 46 nautical miles (85 km) saved.
Time saved: about 3 hours
Fuel consumption per hour: about 1000 litres (285 gallons)
1000 litres cost about 190 US$ (217 €)
3000 litres = 570 US$ (650 €)
This is not yet a big deal, but it is not all.
Charterers pay for the ship about 6,000 US$ (6,840 €) hire per day. So in
three hours it equals to 750 US$ (855 €).
Total amount saved: 1,320 US$ (1,500 €).
Not a big deal as well - in shipping they sometimes do waste far higher
amounts for nothing, but take a ship that performs about 20 such voyages a
year, and take a shipowner having 50 ships on this route, then the choice
between Great Circle and Rhumb Line becomes very important.
More than a million per year - just because of these 45 nautical miles!
And three hours can be crucial in shipping as well: Arriving three hours too
late could mean you just missed the tide in the arrival port, and have to
wait now for 6 hours idle for the next highwater, stevedores could have been
ordered for 8 a.m. and you arrive with your ruddy vase nicely at 11 a.m.
(horrible amounts for so called 'standby-times' - especially in the US), or
due to your late arrival pilots decided to take in another ship instead of
you and you are now waiting one week at the anchorage until she cleared the
berth ... all this has to be taken into consideration.
The consequences are so horrible that we not even dare to think about them.
But never the Captin will be refunded for his economical performance. All
this beautiful money remains with the shipowner and charterer. But if you as
Captain once do not perform nicely, they will not be sparing with 'love
"Explain soonest why you did not ... advise immediately how this could happen
... do really not understand why you ..."
That's nowaday's merchant shipping biz ...
A word to yacht owners regarding Great Circle Sailing:
If you are not a professional or participating in a race you should refrain
from Great Circle Sailing.
The Great Circle usually brings you too much North polewards (or South, when
on Southern Hemisphere) and sudden weather changes can cause you trouble,
According to SOLAS (Safety Of Life At Sea Convention) it is my duty to
assist and rescue you, then.
I will do that with great pleasure.
But picture that with a water temperature of 4°C (39°F) your chance to
survive is only a 40 minutes and it is not very likely that I am always on
the scene just when needed and whether I am able to manoevre alongside you
and pick you up in time.
For a Trans-Atlantic passage, lets say from the Straits of Florida to
Northern Europe, yacht owners should always choose a Southern route, where
more land is close (Bermuda, Azores), the water is warmer and more ships are
underway to assist in case of distress.
Have a nice sailing!
Information about Sable Island obtained partly from:
"Nova Scotia and Bay of Fundy Pilot", Naut. Publication Nr. 59, 12th
Edition, 1991, British Admiralty, Ministry of Defense, Taunton, England
Drawing of the Great Circle Routes obtained from:
"Ocean Passages for the World", Naut. Publication Nr. 136, 4th
Edition, 1987, British Admiralty, Ministry of Defense, Taunton, England