Patent ID: 7877887

Claim:
A method for correcting a bias error, comprising: (a) selecting a sensor having a sensitive axis, said sensor sensing a component vector of a total vector about said sensitive axis, said component vector having a magnitude proportional to a sine or a cosine of an angle between said component vector and said total vector; (b) orienting said sensor in a first orientation that defines a first direction, said sensitive axis defining a spatial reference axis; (c) measuring a set of signals from said sensor while said sensor is stationary in said first orientation, said set of signals being representative of said component vector and including at least one signal; (d) orienting said sensor in a second orientation that defines a second direction, said sensitive axis being substantially parallel with said spatial reference axis, said second direction being substantially opposite said first direction; (e) repeating step (c) with said sensor in said second orientation; (f) alternating between the orientations of steps (b) and (d) and performing step (c) after each alternating to obtain a plurality of sets of signals, said plurality of sets of signals numbering at least three; (g) converting said plurality of signals to a corresponding plurality of component vectors; (h) calculating a plurality of first order corrected component vectors for determining said spatial reference axis based on first order derivatives of said plurality of component vectors; (i) calculating a higher order corrected component vector for determining said spatial reference axis, said higher order corrected component vector being based at least in part on said plurality of first order corrected component vectors and on a higher order derivative of said plurality of component vectors, said higher order derivative being at least a second order derivative; and (j) inferring said spatial reference axis from said higher order corrected component vector.