Magnetic Declination Correction, the Dummy Version

setting magnetic declination

Over the years, we've noticed that more than a few freelancers are a little hazy on the basics of using maps and compasses. The concept of map projections and the resulting coordinates is a total black box for most of them, and the worst of them can't even understand directions... the worst, like eHowian Jeremiah Blanchard. The former art and history student shared his ignorance in the GoneOutdoors.com post, "How to Calibrate a Magnetic Compass."

Nobody around here is quite certain what "calibrate a magnetic compass" means. Some resources talk about certification of a compass, and there is a lot of information about calibrating electronic compasses, but an ordinary compass with a magnetic needle? The closest we can come is setting the declination on adjustable compasses¹, which is where Blanchard went, too. His problem was mostly that he didn't know what he was talking about.

You can tell he was out of his depth by reading his post, which contains miscellaneous factoids and bits of (mis)information such as,

"...magnetic north is approximately 1,000 miles away from the true North Pole, and the distance between these two points can change significantly based on your specific geographic location when using a compass."

In the first place, magnetic north is a direction and not a place. The place is the magnetic north pole, which is not 1000 miles from the geographic north pole (it's more like 1000 kilometers). Second, the distance between the points has NOTHING to do with your location: it's the angle between the two locations that differs. Now comes Jeremiah's instructions for "calibrating" a compass which, we intuit, he believes has something to do with magnetic declination. His steps?

1. Place your compass on a USGS topographic map.
2. "Line up with the true north arrow indicator on the map by placing the heading arrow on the compass in sequence with [sic] the true north line." — We think he means "align the compass arrow with the north arrow on the map." In reality, you'd have to rotate the map, of course, since the north arrow will point north no matter what.
3. "Rotate the compass housing dial until it is lined up with the magnetic north indicator on the map." — We aren't really sure, but we think he's saying to set the declination.
4. "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" bullshit again.

The reality of Jeremiah's bush-league instructions are that he completely ignored the actual calibration step, which entails setting the magnetic declination either from a topographic map or from some other reference. Unfortunately, neither our Dumbass of the Day nor his eHow content editor understood just how poorly Blanchard had botched his assignment. We did, though...

¹ In case you didn't know, not all compasses are adjustable...

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