November – the sextant survives in the navy, & joy in little jobs

I learnt this month that Royal Navy officers still have to learn and practice astro-navigation with a sextant, despite the incredible array of technology at their disposal.

I was at a Zoom meeting with Rear Admiral Peter Sparkes, the UK National Hydrographer, organised by the Suffolk branch of the Cruising Association.

He gave two reasons for continuing to insist on familiarity with traditional navigation on warship bridges: the first is the risk of damage to electronic systems, which is an obvious one in combat; the second is jamming of GNSS satellite signals.

Sparkes did not go into detail, but satellite jamming is a problem which armed forces everywhere are trying to solve. A variant of jamming is spoofing, where the signals are altered, still giving a position, but a wrong one.

The Rear Admiral said he hoped there would be technical solutions soon to the satellite problem. He did not elaborate, but updated versions of ground radio-based navigation systems such as Loran are certainly being revived.

There is also a big development effort to shrink inertial navigation systems to a more manageable size and greater accuracy using electronic and even quantum forms of gyroscopes, to track position by measuring cumulative changes in direction and speed without any need for outside signals. These could prove vital as satellite backups in a whole range of applications, including driverless cars and ships if they are to operate safely.

An article on quantum gyroscopes in this month’s Royal Institute of Navigation journal points out that commercial airlines have never relied entirely on satellite navigation, and always have backup inertial systems. There’s a lesson for amateur sailors: if the navy still has traditional navigational backups, we should all make sure we have them as well.

Meanwhile, it’s been lockdown again, and the boat is out of reach, four hours drive away from where we are living at the moment. There is compensation, however, in some ordinarily dull winter jobs, which have been peculiarly satisfying this month.

I finished making a new canvas cover for the inflatable dinghy, a much smarter version of the original plastic sheeting that came with it when new. That was disintegrating after 16 seasons strapped on deck in summer sunlight. And at last I found the annoying but minute leak in the dinghy, which had been softening it overnight. I patch repaired it.

Smart new canvas cover
Refurbished Dan Buoy, saving £125 for a new one.

After years struggling with the Dan Buoy because it would not extend to its operational height above water of 2 metres, I also brought it home to repair. Someone had grabbed hold of it and bent the tubing when climbing the stern ladder, and the bends were jamming the telescopic mechanism.

It proved impossible to straighten on the boat but on a workbench, after an hour of fiddling, it was operational again. I also made a new red flag because, like the dinghy cover, the old one had disintegrated in the sun.

Then there were little bits and pieces to buy, including a carbon monoxide alarm. We were prompted to finally get one by yet another RYA warning, after two people had been killed by the leaking exhaust of a diesel boat heater.

I’ve bought a new tin of varnish to take to the boat to smarten up the chart table and the bulkhead behind it. A more important job we’re thinking about is buying and fitting a big electric bilge pump, to replace one of our two manual pumps.

Those are big, and manual pumps were fine with a previous owner’s racing crew of 6 or 8. However, you can’t have most or all of the crew pumping in an emergency when there are only two or three: we should have installed an electric one years ago.

The last navigator

Do you really prefer hitech modern satellite navigational gadgets to the romance of the stars and traditional methods, asks a friend? Actually, I think the question raises another: is there really a low tech traditional method in our modern sense of it? For most people, tradition means compass, sextant and chart.

A Micronesian sailing canoe, from The Last Navigator

As I mentioned in an earlier post, I have been catching up with a second hand copy of The Last Navigator by Stephen D Thomas, printed in 1987, which explains exactly how Polynesian navigators have been achieving remarkable feats of accuracy for thousands of years before even the compass was invented, let alone the sextant. The book has underlined for me how hi-tech our “traditional” methods of navigation really are.

A diagram of a sailing canoe from The Last Navigator

For the last 250 years navigators have in reality relied on precision instruments and almanacs full of mathematical calculations of great sophistication. These are methods, materials and advanced technologies that would have astonished the ancients.

A maritime chronomoter, key to longitude measurement, was a major technological achievement of the 18th century, while in its day the modern sextant was a leap forward in precision engineering. It simply was not possible before the 18th century to make instruments of such accuracy.

A great deal of learning and practice went into using both chronometer and sextant, in combination with the immense data resources published in nautical almanacs and the even bigger resource of worldwide nautical charts created by meticulous surveying.

Actually, you don’t even need to learn where all the stars and constellations are to use a sextant. The tables tell you where to look, using your compass and sextant and a rough approximation of how far you have gone since your previous position fix. That surprised me when I learnt how to use mine (a late starter because it was only 20 years ago). There is satisfaction in being able to find and recognise the constellations and the main stars from memory, but it is not at all essential.

Contrast all that with the methods of Polynesian navigators. They are well known to have had no instruments and charts, and to have relied entirely on reading the stars and waves and watching for birds and sea creatures. An aura of mysticism and magic surrounds those achievements. But The Last Navigator brings out the detail of how they actually did it, and it reads as an astonishing feat of memory and long practice, which in its underlying method turns out to connect directly with what we do nowadays.

They used the rising and setting positions of many different stars as their compass; they read information about currents and directions in subtle changes in wave patterns and the surface ripples of water; and bird and sea creature behaviour gave them information about distances from land.

In their heads, they carried the equivalent of a chart of Pacific islands. They fixed their position on it by seeing, in their minds, where lines from the rising and setting points of stars on the horizon intersected, using a reference island chosen for the particular passage they were on.

It was the use of position lines that I found most intriguing. Far from being some unknowable ancient and mystic puzzle, Polynesian navigation essentially did what we do now. Underneath everything was a geometry common to all methods of position fixing. Finding the intersection point of lines from stars and other known objects is the basis of every type of navigational position finding.

Intersecting lines are used by the computer in your GNSS receiver to calculate a position using signals from satellites. “Traditional” navigation using a sextant and chart uses lines measured from precise instrument readings of angles in the sky. For thousands of years Polynesian navigators have achieved a similar feat using no aids at all but memory, observation and experience.

If you want truly to learn to navigate with the romance of the stars and a deep understanding and feel for the natural world, you will have a long way to go. According to Wikipedia, by 2014 these skills were still taught only in the outlying Polynesian island of Taumako in the Solomons.

A new edition of The Last Navigator is still available in paperback, though search now under Steve Thomas, not Stephen D. The charm of the book is that it combines the story of a young man’s ocean adventuring with his quest to be taught the old arts before they disappear.

I also found on Amazon what looks like a much more detailed manual of techniques: We the Navigators: Ancient Art of Landfinding in the Pacific by David Lewis. If I could find a copy for less than £30 I would buy it! There are several blogs for enthusiasts of Polynesian and Micronesian navigation and quite a few replicas have been built to sail.

Philosopher of sailing

The letter below was published in Cruising magazine this month:

If it does not prompt a few cross letters from traditionalists in the next edition, I’ll be surprised, especially after the recent finish of the Golden Globe round-the-world race using sextants and traditional navigation – just as they did on the first race 50 years ago, which was won by Sir Robin Knox Johnston in Suhaili. It was also the race in which the sad figure of Donald Crowhurst cheated in desperation and then disappeared from his yacht.

A victorious Knox-Johnston 50 years ago

Electronics were banned in the anniversary race, though I did read somewhere that they all had to sneak in a satellite phone just in case.

If the old guard don’t complain about my letter, then things have changed more than I expected….


PS I know I’m more than old enough to be part of the Old Guard, but I think modern electronic navigation is wonderful, and it leaves more time for actually handling the boat.