April 24, 2014

Miracle-making satellites

IT’S STRANGE how ordinary people sometimes suddenly become infatuated with the idea of buying a yacht and sailing around the world. The first question they ask, before they actually plunk down any money, is: “How safe is it?”

Well, it’s as safe as you make it, of course, but I’d say that it has become significantly safer in my lifetime, which is, admittedly, quite a long time. And what has brought about this significant change? Satellites.

Thanks to satellites, two of the greatest safety factors for small sailboats crossing oceans, or even plying coastlines, are Epirbs and GPS. If I had to choose one as the greatest aid to safety, I’d have to plump for GPS. Epirbs are wonderful at getting you rescued after you’ve gotten into trouble, but GPS is what keeps you out of trouble in the first place.

It seems inconceivable now that anyone would attempt to cross an ocean without GPS, but many thousands of people did it before the rocket scientists got good enough to send up satellites. I well remember the first time I navigated across the South Atlantic to Rio de Janeiro on a racing sailboat.

I relied on dead reckoning for the first couple of days out of Cape Town, but the time came when I had to take the sextant out of its box and demonstrate to a skeptical skipper and crew that I knew how to handle it. I was the only one aboard who had any idea of how to reduce a sun sight, and to tell the truth it wasn’t much of an idea, since I had been teaching myself from Mary Blewitt’s little book, and I’d never taken a sextant sight at sea before.

My first effort produced a position that was a long way away from my dead-reckoning position. It was, in fact, about 15 degrees away. That’s about 900 miles. I was horrified. I didn’t let anyone else see my workings and I didn’t tell them anything while I checked and re-checked and consulted Mary Blewitt again.

Nothing seemed wrong with the figures, which made me even more anxious. I began to wonder if I could dead-reckon all the way across the ocean. Then, out of the blue came one of those rare bolts of brain lightning. Fifteen degrees was the amount the sun traveled in one hour. I had used Cape Town time instead of Greenwich Mean Time when taking the relevant figures from the Nautical Almanac.

I reworked my sums and the new position came out reasonably close to the dead-reckoning position. The skipper and crew were satisfied, and I was very smug. I had no more trouble all the rest of the way to Rio.

Years later, just a few years back in fact, I was singlehanding in the Pacific, running down the west coast of Vancouver Island, British Columbia. I ran two miles offshore for the whole day in dense fog. I saw nothing but one startled seagull sitting on a raft of seaweed. I was navigating with a handheld GPS, of course,  plotting my position on a paper chart every hour. My nice sheltered anchorage turned up just where I expected it to be, and lo! it was in bright sunshine.

I would never have dared to do that 40-mile trip in the old days before GPS. These days, we have all become  accustomed to having our position available on demand at all times in all conditions, and few of us realize what an incredible change this has made to small-boat navigation. I still regard it as a miracle, and not a minor one.

Today’s Thought
Miracle comes to the miraculous, not to the arithmetician.
— Emerson, Conduct of Life: Worship

Two houseflies met on the ceiling of a luxury apartment.
“Aren’t humans strange?” said one.
“They sure are,” said the other, “but what made you mention it?”
“Well, I was just thinking — they spend a small fortune building a lovely ceiling like this, and then they go and walk on the floor.”

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)


Matthew Marsh said...

One of my favourite things about GPS is the reactions you get when its workings are explained to someone for the first time.

Somewhere around the point where you say "And this is the calculation to correct for the difference in the speed of time itself between your position and each satellite's position", there's usually a long pause. Followed by some variant of "This is absolutely incredible."

John Vigor said...

It is indeed absolutely incredible, Matthew. The whole GPS thing, I mean. And I can hardly believe the equipment needed to work it out and display the result is small enough to fit in the palm of your hand. Or even smaller in some cases. I wonder what Capt. Joshua Slocum would have thought of it. You don't even need a one-handed alarm clock to help you find your longitude these days.

John V.

Bill said...

I casually consult GPS on land-bound trips on the interstate, and get cheesed off when it is not INSTANTLY available.