I’m sure most are aware there are two North Poles: The True North Pole, the one based on the spin of the earth, 90 degrees North. This is the top of the globe.
The other is the Magnetic North Pole. This one is based on the Earths magnetic field and is the North Pole all compasses use. And, it moves. It’s currently projected to be at 86 26′ N by 175 20′ E. Projected, because to know for sure they have to send some poor SOB out there with a compass to see if it points straight down to the ground. Not somewhere I want to go. It does appear about every 10 years someone draws the short straw and goes to hunt it down.
When navigating, you specify your heading as True (T) Magnetic (M), or relative (R). Electronics allow you change your preference on the fly. They do the calculations for you and are aware the the variations for your location. Compasses only show magnetic. All paper charts (maps are land, charts are water) has a compass rose and shows the variance in the region.
This is covered over and over again in every sailing and navigation course / seminar I’ve attended. Then, I ignore it all.
Even though the poles are way off, there is a line where they match up and the variance is zero. As luck has it, that line pretty much runs through Central Illinois. Chicago has less than a 1 degree variance. Insignificant and irrelevant for my purposes.
Not so where I’m at now. Last night in the dark and fog, I was using my instruments more than normal and nothing was adding up. My course showed 100, yet my longitude kept increasing, when it should have been decreasing. I scratched my head and remembered variance. I looked it up and where I’m at there is over a 20 degree variance.
Sorry for the tech-no-babble, but I thought some might find it interesting. No pictures today, just fog and cold.
Kurt & Sue Sail 