  A method to construct an observability-constrained magnetic-field-aided
inertial navigation system is proposed. The proposed method builds upon the
previously proposed observability-constrained extended Kalman filter and
extends it to work with a magnetic-field-based odometry-aided inertial
navigation system. The proposed method is evaluated using simulation and
real-world data, showing that (i) the system observability properties are
preserved, (ii) the estimation accuracy increases, and (iii) the perceived
uncertainty calculated by the EKF is more consistent with the true uncertainty
of the filter estimates.
