Algorithm 2 Improved Initial Alignment Algorithm

Require:  $k=0$; Coarse alignment time $T_{coarse}$; Total alignment time T   1: if $k\ge 1$ then   2:    if $k<T_{coarse}$ then   3:        Denoise the inertial sensors’ information with the ELMEMD-Shannon method;   4:        Coarse alignment based on solidification coordinate frame;   5:    else $T_{coarse}<k<T$   6:        Fine alignment with the RHCKF filter;   7:    end if   8: end if   9:return Output the alignment results