Friday, February 25, 2011

Magnetic Compass Conundrum

You might have read (or heard) something about the Earth's magnetic pole shifting at an increasing rate, which causes compasses to point in the wrong direction.

Technically true. Like "climate change" this is something that has always happened and always will happen in the future. The Earth's magnetic pole is directly related to the movement of the magnetic field, which in turn is related to movement on Earth's liquid iron core. The core continually transfers heat, thereby creating a naturally occurring electrical conductor that creates the magnetic field. So just to be clear about this — what's happening has nothing to do with the end of the Mayan calendar on December 21 next year, or anything else so dramatic. This is nothing new, but the folks who write the news have to have something to talk about and this sounds pretty big, so they write about it.

For the record, the shift in magnetic pole position amounts to about 1 degree every 10 years. So if you're out hiking for the next 30 years, you'll see a 3-degree shift on your compass. Whoopee!

The reason I say Whoopee is because nobody, regardless of how good you are with a compass in hand, is steady enough to be flawless when using a magnetic compass for navigation. At best, you'll be a few degrees off anyway as you navigate your way through brush and trees and around lakes  and detour around canyons. This isn't brain surgery. You use a compass to maintain a general heading toward a desired point. Then you shoot another bearing and head off in that direction. You take compass readings on visible landmarks, walk to that landmark, then shoot another bearing to the next one. Over and over again, you repeat the process to enable you to hike in the general direction toward your destination, continually making adjustments as you sidetrack around obstacles. So maintaining a precise bearing to the very degree is not only unnecessary, it's also impossible.

If you're out on the ocean, the boat will bob and weave with very motion of the water and wind, not to mention the effect of current. The fastest way to go blind and nuts at the same time is to stare at the compass and keep your hand on the helm, trying to steer a perfect course. Celestial navigation was invented to keep mariners from going blind and nuts. With celestial navigation, a sailor takes a sighting on the sun or moon or stars once per day (or night), makes calculations based on published tables for precise times each day. Then adjustments are made to the heading to correct the course. Same goes for use of a GPS — it's only a method of taking a "fix" on your location so you can compare that reading with the map to see where you are relative to where you want to go.

And my point is? My point is that regardless of what you hear or read or see on the news about how you're going to get lost because the magnetic pole is racing toward Siberia, don't worry. You won't get any more lost than you ever would before.

That said, I think everyone who ventures into the outdoors should carry a detailed topographic map of the area and a quality compass. More important than that is to know how to use those tools. If all you ever rely on is GPS, the day will come when that system will fail you (probably because of dead batteries), and then you really will be lost.

Carry a map and compass. Know how to use them.


  1. I do carry maps, and a compass, but in truth, I seldom wander so far anymore that I can't find my way back to camp.

    The battery on my new GPS is good for about four hours so if I wanted to rely on it I would set a waypoint when starting out for the day and then turn it off to save the battery.

    If I needed it later I would turn it on to point to my waypoint so I would know which general direction to travel.

    If I'm in a real brushy area I mark my trail as I go along being as my only concern anymore is getting back to camp or my boat.

    What I wonder about is how birds and butterflies figure it all out.

  2. Now that I think of it, as far as I know, birds and butterflies do not fly all night long so maybe they depend more on visual navigation.

    Oh hell, now I'm wondering about fish.

  3. Land navigation is definitely a perishable skill, and I agree that knowing how to use a map and compass properly (and if you're really cool a protractor and an understanding of the G/M angle on high speed maps) are more important than a slight shift in magnetic north. A decent quality map that has been recently produced should be updated with the current magnetic north, and some maps even tell you how to calculate the yearly drift. But none of that really matters if you don't know how to use your tools. You can still get super lost even with a map. Not that I ever have, but there was this one time...well it looks like I'm out of room. But, yeah, practice is definitely important.