High Latitude Fun

So I looked some more at the data the magnetometer was giving me. For a while I thought that the X, Y and Z axis might not be aligned the way I thought they were or in the most logical way. The reason I thought that was that the Z-axis was registering some 4 times higher than X or Y. I knew it wasn't a calibration issue because I could re-orient the device that the large reading would move. I figured the large reading HAD to be due north. NOPE! The larger reading on Z was exactly what it said it was: a big magnetic field straight DOWN. WTF, I thought? Localized field? I took the device outside and there was no change.

Finally, after some looking I happened upon the USGS National geomagnetic Program website. They actually have models of the Earth's magnetic field. There is this applet that lets you select a model (they update every five years) a latitude and longitude and the current time. It then dumps out the predicted X, Y, and Z field strengths. Sure enough, the predicted value in Z was 52000 nT down and only 18ooo nT north. I had no idea the Earth's magnetic field tilted so early.

Its good to have confirmation of my readings. It was kind of a eureka moment when I ran that modeling applet. However, after that died down I realized that it kinda sucks a little in that much of the field strength is in a direction I can't use for navigation. Wait. Or is it? Hmmm. Thinking in a post is probably not good. However, just this moment it occurs to me that on the basis of the model I know which direction the Earth magnetic vector is suppose to point. That vector has a simple relationship (two rotation operations) with the "North" direction. That should fact should be usable and allow me to maintain my measurement resolution. I'm having trouble coughing up a sentence that expresses my thinking so I'll stop trying and post it later.