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2011-02-09

Variations on a theme





Now I realize how out of fashion the lowly and ancient magnetic compass is in light of the New Dispensation of GPS, but I still like to call myself Hornblower, crow out "helm's a-lee!" and refer to the little Plastimo compass in the cockpit with seamanlike purpose. In fact, I use it to, you know, navigate. I have bearings to my favourite destinations more or less memorized, which is what happens when you play with charts. The Ritchie Globemaster with the amusingly named Soft Iron Compensator Balls in the steel boat is, contrastly, almost too grand to consult...I feel like I'm taking penicillin to the Norwegian Resistance when I look at its sober, monastic dome. It's about the most professional gear aboard and it says This is the Vessel in Question.

Anyway, geomagnetism and its role in navigation continue to attract my attention, even more than "do you know how to rewire an alternator?". Which to be honest, is probably something I should pick up.

Nonetheless, on my local chart, the compass rose says, as they do, something along the lines of "10 degree W deviation (1994)". That means if I read 90 degrees on the compass, it's actually 80 degrees T. It also suggests that the last time someone was around here with a Great Big Azimuth Compass was pushing 20 years ago.

Unfortunately, the stately and predictable movements of our Magnetic North Pole are becoming...well, skittish, and the rate of deviation (also marked on most charts) is probably undervalued.

Does this affect the average sailor? No. When it hits 11 deg. W in my home waters is unlikely to affect my helming or pilotage as I can't steer better than a 5 deg. wobble most of the time. Nor would I want to.

But I have found it interesting that there are starting to be real-world effects due to the Wandering Pole:

http://www.physorg.com/news/2011-01-tampa-airport-runways-renumbered-due.html


"The primary runway at the is designated 18R/36L, which means the runway is aligned along 180 degrees from north (that is, due south) when approached from the north and 360 degrees from north when approached from the south. Now the (FAA) has requested the designation be changed to 19R/1L to account for the movement of the magnetic ."

My government has something to say about it, as well. "During the last century the Pole has moved a remarkable 1100 km. What is more, since about 1970 the NMP has accelerated and is now moving at more than 40 km per year. If the NMP maintains its present speed and direction it will reach Siberia in about 50 years." Oh, Canada, we've already given up on Hans Island...must we have our little lodestones pointing to a kleptocracy, now?

I point this out as a navigational curiosity and as a small token that the Earth doesn't really care what is printed on our charts.

It's very cold, windy and bleak here at the moment and it's hard to do much aboard. I pushed off a great deal of snow from the deck yesterday, but even with the anti-skid, it's hard to stay upright. The weather is forecast to go above zero C. next week, so I will try to resume refitting operations. The good news is that I believe I've found a way to "deroof" the pilot house without leaving the boat entirely open, and this method will allow welding on deck in dry circumstances.

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