Magnetic Compasses for the Dummy Outdoorsman

Magnetic declination rosette

After several years of correcting the utter bull published by ignorant but greedy freelancers, you might think we'd have become inured to the stupidity endemic to the breed. Not so: every day introduces our staffers to even more clueless journalism, history, and English lit students trying to write about the science they've avoided studying. Sometimes we wonder if physics and chemistry students freelanced about writing romance novels and interpreting poetry.¹ Be that as it may, today's nominee is art and history graduate Jeremiah Blanchard, whom we found attempting to explain "How to Calibrate a Magnetic Compass" at GoneOutdoors.com. Unfortunately, he couldn't...

...he couldn't because, although Blanchard never mentioned it, you can't "calibrate" a magnetic compass: unless demagnetized or otherwise damaged, a magnetic compass needle will always point at the north magnetic pole. Jeremiah then informed us that,

"To calibrate a compass properly, you must understand that magnetic north and true north are not the same directional value. In fact, magnetic north is approximately 1,000 miles away from the true North Pole..."

Well, he was right that the geographic and magnetic poles aren't the same place, but he was wrong about that "approximately 1,000 miles" number: the difference is somewhere around 500 kilometers, which is more like 300 miles. Nevertheless, Jerry's ensuing information was partially correct:

"This phenomenon is referred to as 'magnetic declination' and requires you to adjust your compass while using a map that features both magnetic and true north directions."

Other than the facts that magnetic declination is not a "phenomenon," and that you always need to correct for it, that's correct. It's from this point on that Jeremiah's "help" went off the rails. Rather than explaining how to set the declination on a compass, which is about as close to calibration as magnetic compasses get, he typed out a set of instructions for using a USGS topo map, including:

• "Line up with the true north arrow indicator on the map by placing the heading arrow on the compass in sequence with the true north line." — We guess he means "parallel to" there.
• "Rotate the compass housing dial until it is lined up with the magnetic north indicator on the map." — Ummm, dude, you can't "line up" a dial: it's round.
• "Keep the compass in place and then rotate the map until the compass needle is pointing north in sequence with the magnetic north line."  — There's that "in sequence with" crap again. And, to reiterate, the needle always points north.

Jeremiah cribbed those instructions from a blog, even though he claimed to have used the USGS website (he didn't). However, what's most irritating is that he didn't say how to "calibrate" the compass, by which he apparently meant "set the declination." The method differs from compass to compass, which is why his instructions are useless. What he really should have done was point the reader to the NOAA website for determining declination (the declination on a USGS topographic map is out of date by the time the map is published) and then to instructions for setting the declination for a representative compass.

But that would  have required knowing what he was talking about, and our Dumbass of the Day couldn't meet that criterion.

¹ Probably... we don't know.

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