29th March 2017 – Man is Not Lost – Tom Cunliffe

Back to CNYC for a third time, Tom both celebrated and lamented the astounding developments in navigation over his lifetime. It is to celebrate because knowing effortlessly where you are on the planet to within a few feet is of course remarkable and wonderful. But it has its pitfalls, and he wondered whether one will ever get the same satisfaction and understanding from “pushing buttons”, as one used to get from using nous and skill to work out where you are, and which way to go – or, of course, not go.

We have, he ventured, become fixated on expectations of accuracy. Fishermen of the 1850s would never have seen a chart, and probably carried no compass. They could read the sea and the sky, and with the knowledge handed down to them by their forefathers and by judicious swinging of the lead, carrying tallow to pick up a bottom sample, they went about their business day after day in all weathers. Now, glued as we are to our phones, chart plotters and echo sounders, we think we always know, and always need to know, exactly where we are to within a cockpit’s width.

With a sextant, a trailing log, and an accurate timepiece one can ascertain where one is on the planet to about a quarter of a mile. To many of today’s sailors, that sounds hopelessly inaccurate. But to be within a quarter of mile is fine. We used to be proud to find we were within quarter of a mile of where we computed we were. We would then take a look out of the cockpit, check the echo sounder, take sights of landmarks or buoys and refine the fix.

Tom recounted a nice tale of navigating from Rio to Barbados, armed with a very large scale chart, a compass, a sextant, a Smith and Wesson .38 (don’t ask) and a wristwatch. He was encouraged to make the voyage so ill-equipped as going back to jail in Rio was even less appealing than setting off. He had managed to write down the latitude and longitude of Barbados, and had a few pilotage notes. Unfortunately he lost the watch overboard somewhere, so lost any means of assessing his longitude. But this wasn’t the catastrophe it might seem. He kept going until (by sextant) he was at the latitude of Barbados. Then all he had to do was turn left (obviously, as Africa was to the right) and sail the line of latitude until he spotted Barbados. Neat, eh! He didn’t know where he actually was, but the key thing is: he didn’t need to.

There are some real pitfalls awaiting the mindless user of GPS and chart plotters. One can easily mistype or misread the coordinates of a waypoint (especially if close to a whole degree of longitude, west of Greenwich). He told of a Yachmaster candidate who determinedly took him into the wrong estuary because of a waypoint error, despite all the visual evidence to the contrary. Another problem is that chart datum may not be right so although the GPS is accurately giving lat and long, it thinks the land is somewhere other than where it actually is, thus allowing a chart plotter to show you, with apparent great accuracy, approaching a harbour by road. Not to mention charts still based on century old surveys… Then there is the siren of the vector chart. The alternative, a raster chart, is a digitised paper chart so everything marked on the paper chart is there to see. But a vector chart is a database of things and their locations and the image is created for you by software. It doesn’t show detail in a zoomed-out view. There wouldn’t be room for all the symbols. And who zooms in on apparently empty bits of sea, all the way along a passage? Not enough of us do, apparently, and Tom is called as an expert witness from time to time when a navigator claims something he hit (like a reef) “wasn’t on the chart”. It depends, y’see, which chart one is talking about.

The answer? Buy and learn to use a sextant. Do the dead reckoning. And most important? Keep a logbook. By all means use the electronics but don’t treat them as gospel, compelling though they are.

A salutary talk, and a great evening’s education and entertainment.

RB