I was intrigued by the equipment list below, which is more than three decades old, because it was a reminder of how long we have been arguing about the risks and rewards of electronic navigation. I found the list in some old files I was checking last year for the sixth edition of Pass Your Yachtmaster by David Fairhall and Mike Peyton, which I was commissioned to update by Adlard Coles*.
The list was part of an article I produced for the Guardian newspaper about electronics for small boat navigation, under the headline ‘And a satellite to steer her by’, researched by talking to manufacturers due to appear at that year’s London Boat Show. I had forgotten all about it.
How accurate is the position calculated by your smartphone? As mentioned in the previous post, the Royal Institute of Navigation is sceptical. Its new book on electronic navigation for leisure sailors says: “At sea, mobile phone positioning uncertainty will typically be several hundred meters or more, which may be enough to put us into danger”.
I am looking for some proper studies on this issue, because I am sceptical about that statement. In the meantime it’s easy to check what your phone tells you about its own location performance when it relies only on satellite signals.
The Royal Institute of Navigation’s excellent new book on electronic charting is pretty tough on the use of smartphones as chartplotters, claiming their accuracy can be as poor as 200 metres or worse. I think they may be out of date on this narrow point of phone accuracy, which I’ll come back to in a later post. But in the meantime I’ve had a demonstration of a different smartphone problem, one I had not focussed on before: unreliability in cold weather.
One of the nicer things about lockdown (if there are really any at a time of rampant virus) is to go most days for long walks in the winter cold, which is how I discovered that my phone seriously dislikes low temperatures. Not just sub-zero, but any day with temperature near or below zero. When there’s a strong, chilling wind it even goes on the blink in an outside pocket with the temperature in high single figures.
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.
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. Continue reading “The last navigator”
Two letters in the latest issue of the excellent Cruising Association magazine* claim it is now safe to rely entirely on electronic charts because backups to the boat’s main chartplotter are so cheaply available. You can leave your old paper charts abandoned in the bottom of a locker somewhere, the argument goes.
However, while researching updates for the yachtmaster book I mentioned last month, I’ve been re-reading intensively about old fashioned navigation techniques I learnt a long time ago, some of which were beginning to fade from memory. It has reinforced for me how important it is to avoid total reliance on electronics and have a portfolio of navigation skills including the old ones. Continue reading “Relearning old navigation lessons”
The British government turns out to have been ahead of the game on the satellite risks I mentioned last month, with a £36 million programme just announced to prevent navigational satellite failures damaging the economy by as much as £1 billion a day. It is feared that the entire country has become over-dependent on a handful of satellite systems.
Emergency services, the energy grid, mobile phones, Satnav, broadcasting and other communications, the Stock Exchange and an array of other activities all rely heavily on the super-accurate timing provided now by navigational satellites such as GPS and similar systems. There are life-threatening risks from failure, says the government.An image of a third generation Lockheed Martin GPS satellite
The new investment is in a National Timing Centre to create a network of super-accurate atomic clocks around the UK, accessed through ground-based communications, so that the economy will no longer be over-reliant on timing from GNSS signals from the sky.
GNSS is the term that embraces the US GPS, the first system, Russia’s GLONASS satellites, Europe’s new Galileo and also a rapidly developing Chinese system.
Galileo failed completely for a while last year during its start up phase, because of operator errors, and there are now many examples of interference with GNSS systems and malicious ‘spoofing’, in which navigation instruments are fooled into thinking they are somewhere else. The heart of all navigation by satellite is accurate timing, without which positions cannot be fixed.
At the Royal Institute of Navigation’s small boat conference in Lymington earlier this month, I learnt a lot about new risks of error in satellite navigation : I did not know, for example, that it is possible with quite cheap local equipment to fool the GPS on a plane, ship or even a missile into thinking it is somewhere other than its real position.
There are now tens of thousands of reported incidents of errors, deliberate, accidental or of unknown cause, with a substantial number of them unsurprisingly in sensitive areas such as the Gulf, and the Black Sea near Ukraine, suspected to be hostile activity.
Reports of accidental errors include a couple of local failures when US naval vessels arrived in the port of San Diego, apparently forgetting to switch off unspecified electronic equipment, which interfered with satellite-derived positions for miles around.
Footnote to cruising the Scillies: piloting there is a reminder of the importance of proper Admiralty charts, because they show the age of the surveys on which they are based, unlike any of the proprietary ‘vector’ charts available on chartplotters.
The Scillies is a mixed area from this point of view. Some of the surveys of the area were last done in 1860 – 1904 by lead line, probably from boats carried on naval survey ships and rowed up and down in straight lines quite a long way apart, so rocks could easily be missed. Other parts of the islands were surveyed at a range of different dates in the 20th century.Continue reading “Is your chart relying on an 1860 survey?”
Several earlier posts covered inaccuracies in charts. Last week I came across yet another example in Cala de Portinax, a bay at the north end of Ibiza in the Balearics. This screen shot from my Navionics chart shows depths in a fair amount of detail: yet the numbers were wrong by a factor of three or four. Because of the modest depths shown, we motored in with great trepidation in Olivia Jane, a Beneteau 43 with a 2 metre draft. Yet we found the depths in the middle of the bay were all in the 11-13 metre range and even close in to the rocky shore we anchored in 8 metres. In contrast, the C-Map chart on the cockpit plotter gave no depths at all inside the bay, which is a safer option than mistaken information. We’ve fed this back to Navionics and await a reply, but the nagging question will always remain in future, even if this proves to be a rare mistake: can we trust the inshore information on these charts? What if the mistake had been the other way, showing 11 metres when only 2 metres was there? Do other brands of charts have similar errors? Continue reading “Chart errors (contd).”
Tip for nautical parents and grandparents: great new facility opened this week at the National Maritime Museum in Greenwich – a new play area for children complete with pirate dressing up clothes and lots of games for two years old and upwards, plus a large buggy parking area. Makes a visit to the nautical collections fun for every age. Child approval rating in our test this week was 100 per cent.
We finally managed to take in the excellent Ships, Clocks and Stars exhibition at the National Maritime Museum, Greenwich, which runs only until 4 January. Among other things, it puts the record somewhat straighter on the eminent 18th century Astronomer Royal, Nevil Maskelyne, chief villain of Dava Sobel’s best selling nautical history of the race to measure longitude at sea. Maskelyne was the man who conspired against John Harrison, the genius who built the first true chronometer, or so the narrative goes in Sobel’s book, Longitude.