Bushnell Back Track D-TOUR


I purchased a Bushnell Back Track D-TOUR, partly because it appeared to have a useful digital compass.

The digital compass turned out to be a major disappointment . The documented calibration procedure made little difference, it was still commonly more than 10° in error (not due to nearby magnetic objects, or T/M variation).

The documented calibration procedure calls for holding the compass flat and passing it around a figure-8 path. This would seem to expose the internal magnetometer to flux variation in only one axis (as it is probably mounted flat on the PCB).

Expecting that it might actually be a 3 axis magnetometer, I have trialled calibration by rotating it through 360° in three axes. At first, it seemed to have improved accuracy, but a carefull check shows that the compass indicates anywhere up to +/- 15 ° of the correct reading. A dead giveaway is that rotating the compass exactly 180°  results in an indicated value with up to 40° error.