Friday, July 8, 2011

Underway Still

20117 07

39 59N
040 53W

Less than ten degrees of longitude separate us from our destination. At this latitude a degree of longitude only measures 46 nm in length so we are inside 500 nm away.

All on board are pleased with our progress the more so since the loveliest breeze has blown up. For two days now Meredith has been bathed in the gentle clockwise flow of air around the core of our old nemesis, the Moriary of sailors hereabouts - the mid Atlantic High. Although we are just one isobar removed from the centre, and from the charts I see less than that actually , it is enough distance to grace our deck with the merest caress of air.

It may be only 7 knots but it was welcome for all that. We make 5.5 knots with the cruising chute bent on and light seas surrounding us.

The sailing for 48 hours has been delightful.

Yesterday we came upon a Spanish fishing vessel. Under EU rules such vessels need not carry AIS transponders until January and the skipper of this largish fisher preferred to keep his money in his pocket, perhaps certain that the price of the electronics would continue the downward trend it had carved for itself over the past two years.

As a result the fisher was heard not detected. It can be disconcerting to hear the unmistakable sound of machinery operating when you are gently moving along the middle of an ocean. Sound is not easily followed to its origins out here and it was several long minutes before either the Budget Committee or I could find its source.

As it crossed our bow and we moved to avoid what seemed obviously to be the line it was busily letting out behind itself its captain called on VHF 16.

A pleasanter call could not have been shared between two strangers. The skipper thanked us for avoiding his line. He was fishing for shark and had not seen us until he was upon us. We demurred and assured him his conduct was neither aggressive nor offensive and that more than adequate room had been available to all vessels. He inquired into our destination and left the air for a few minutes. Returning after a short delay he gave us the latest weather from his professional weather routing service.

In all it was a pleasant interruption to the mundane sameness in which we had found ourselves immersed.

Now we wonder how the Spanish prepare their shark.

Length of Longitude

It is a fact of maps that a minute of latitude is always and forever a length of 60.1 nautical miles. This is one of those delightful physical quantities known as a "constant".

Although also measured in degrees broken down into minutes and further subdivided into seconds longitude is not constant. Only at the equator is a minute of lontitude equal to 60 nm more or less.

As you move North or South on the globe from the equator the length of a degree, hence also a minutea and second, of longitude shortens until, at the polish extremities it shrinks to a mere point - having no dimensions whatsoever.

Here is a chart I made up and keep in my ready reckoner for quick reference. It is good enough for on the fly calculations:

Latitude Length of One Degree
(in nautical miles)
0 60.01
10 59 nm
15 58 nm
20 57 nm
25 54.5 nm
30 52 nm
35 49 nm
40 46 nm
45 42.5 nm
50 39 nm
55 35 nm
60 30 nm

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