August 18, 2015

GPS's unfortunate downside

 AS A NAVIGATOR in the dark days before GPS, I used to do a lot of guessing. Most of it was informed guessing, however. I had my reasons.

For example, I discovered that a right-handed helmsman sailed a course farther off the wind while on the beat on the port tack than did a left-handed helmsman. The opposite applied when the boat was on the other tack. The left-handed helm was using his right hand on the tiller, his weaker arm, and so the boat rounded up more in the gusts and carved a course closer to the wind. The right-handed helm was able to use his greater strength to apply more weather helm to stay on course.   

The reason I knew this was because, in between sextant sights, it was the navigator’s task to keep a dead reckoning plot. But he couldn’t stay awake in the cockpit day and night to check that the helmsman was following exactly the course he had been given, so he asked the cockpit crew at the end of every four-hour watch to estimate what their average speed had been and what average course they had sailed. This information was then plotted on the chart to give a dead-reckoning position.

In the ancient days of commercial sail they used a traverse board for the same purpose. It was a very clever little device that allowed the navigator to see at a glance the speed and course the ship had covered during the last watch. It was nothing more than a wooden board with a compass rose on its face and 32 radial rows of holes. Every half-hour, when the sand-glass was turned, the helmsman placed a peg in the hole of the compass point that matched the average direction the ship had been steered during the last 30 minutes.

At the same time, the crew ascertained the ship’s speed on a chip log, and a peg was placed in the appropriate hole on a special speed grid. So the navigator could now come on deck and see what had been happening in the way of speed and direction while he was down below, allowing for all the zigs and zags and wavy wake lines.

He would make a note of these averages and start guessing about leeway and current and a few other things that his instinct supplied corrections for, and then he could plot a dead-reckoning position on a chart. Then all the pegs were pulled out of the board for the next watch to play with.

Nowadays, with all those clever satellites twinkling away in the sky, there’s no need for a traverse board or dead reckoning. GPS does all the grunt work and makes navigation so easy that nobody has any respect for the job any more. Ordinary foredeck hands used to step back in awe when the navigator came strolling along jauntily with his sextant box under his arm and a roll of charts in his hand. Skippers used to address navigators with civility, offer them drinks, and treat them almost as if they were human. No longer, I’m afraid. All that has gone. GPS is very clever, but it has a lot to answer for.

Today’s Thought
Navigation is what tells you where you are, and, what’s just as important, where you aren’t.
 — John Vigor

“Why do all those cows in Switzerland wear bells around their necks?”
“Dunno. Maybe it’s because their horns don’t work.”


Alden Smith said...

I agree that something of the old world sailing tradition and skill has been lost, along with the romance of it all, but if I was trying to make my way among the low lying Tuamotu Atolls on a stormy night I would choose a GPS everytime!

Sixbears said...

It's all very clever until the happy blinking lights go dark. Then it's back to the bad old days of not really knowing exactly and hoping for pretty close and good enough.

Brian Vandersall said...

I am glad I learned navigation the old way (60D=ST) even if I rarely use it.