Ok, I isolated the steering issue I was having. The digital compass was jumping over a range of about 60 degrees. I believe it was because the compass was not completely level which I know is an issue. Digital compasses which compensate for tilt are out of my price range, though, so I may need to rig up some sort of tilt adjustment. But, the Sparkfun course looks pretty level, so probably not a big issue.
A pair of 2D compasses, mounted at a 45-degree angle, might give you tilt compensation without the accelerometers or gyros that the expensive tilt-compensated compasses use. That should give you four numbers which, in a nice little matrix, could allow you to determine how much of the vertical field component is leaking into each of the horizontal components.
Maybe.
thanks Aret, that sounds cool. I’ll have to give that a try on the bench.