Abstract—This paper presents an algorithm for navigating in
challenging indoor environments that do not have WiFi. Deadreckoning
(DR) based on off-the-shelf smartphone sensors and
magnetic matching (MM) based on indoor magnetic features are
integrated. For DR, we utilize a two-filter algorithm structure and
multi-level constraints to navigate under different human motion
conditions. For MM, we use several approaches to enhance
its performance. These approaches include multi-dimensional
dynamic time warping, weighted k-nearest neighbor, and utilization
of magnetic gradient fingerprints. Furthermore, realized
that the key to enhance the DR/MM performance is to mitigate
the impact of MM mismatches, we introduced and evaluated
two mismatch-detection approaches, including a threshold-based
method that sets the measurement noises of MM positions based
on their distances to the historical DR/MM position solutions,
and an adaptive Kalman filter-based method that introduces
the estimation of the innovation sequence covariance into the
calculation of the gain matrix instead of adjusting the measurement
noises. The proposed mismatch-detection mechanism
reduced the DR/MM errors by 45.9%–67.9% in indoor tests
with two smartphones, in two buildings, and under four motion
conditions