Algorithm 1. Pseudocode to detail the orientation estimation process for each SFA.

for each pair of MIMUs (Xsens, APDM, and Shimmer)   for each angular rate condition (slow, medium, fast) remove the static bias for each gyroscope compute the starting orientation for each MIMU initialize the matrix $\mathit{e}$ (#rows = length(${\mathit{p}}_{\mathbf{1}}$), #columns = length(${\mathit{p}}_{\mathbf{2}}$))  for each value ${\mathit{p}}_{\mathbf{2}}$ belonging to ${\mathit{p}}_{\mathbf{2}\mathit{v}\mathit{e}\mathit{c}}$ between [$0$, $uppe{r}_2$]  for each value ${\mathit{p}}_{\mathbf{1}}$ belonging to ${\mathit{p}}_{\mathbf{1}\mathit{v}\mathit{e}\mathit{c}}$ between [$0$, $uppe{r}_1$] compute the absolute orientation of each MIMU separately with the SFA under analysis to obtain ${\mathit{q}}_{A_{\mathit{G}}}$ and ${\mathit{q}}_{{\mathit{B}}_{\mathit{G}}}$ refer ${\mathit{q}}_{A_{\mathit{G}}}$ and ${\mathit{q}}_{{\mathit{B}}_{\mathit{G}}}$ to the starting orientation to obtain ${\mathit{q}}_{\mathit{A}}$ and ${\mathit{q}}_{\mathit{B}}$, as done in (1) compute the absolute orientation error of ${\mathit{q}}_{\mathit{A}}$ and ${\mathit{q}}_{\mathit{B}}$ separately using the gold standard ${\mathit{q}}_{\mathit{S}\mathit{P}}$ to obtain $\Delta {\mathit{q}}_{\mathit{a}\mathit{b}\mathit{s} \mathit{A}}$ and $\Delta {\mathit{q}}_{\mathit{a}\mathit{b}\mathit{s} \mathit{B}}$, as done in (2) convert $\Delta {\mathit{q}}_{\mathit{a}\mathit{b}\mathit{s} \mathit{A}}$ and $\Delta {\mathit{q}}_{\mathit{a}\mathit{b}\mathit{s} \mathit{B}}$ into angular rotation errors to obtain $\Delta {\mathit{\theta }}_{\mathit{a}\mathit{b}\mathit{s} \mathit{A}}$ and $\Delta {\mathit{\theta }}_{\mathit{a}\mathit{b}\mathit{s} \mathit{B}}$ compute the average value between the two absolute errors to obtain $\Delta {\mathit{\theta }}_{\mathit{a}\mathit{b}\mathit{s}}$ compute the RMS of $\Delta {\mathit{\theta }}_{\mathit{a}\mathit{b}\mathit{s}}$ considering only the dynamic parts of the recording to obtain $e_{p1, p2}$ add $e_{p1, p2}$ to the matrix $\mathit{e}$  end  end find the optimal region of $\left({\mathit{p}}_{\mathbf{1}\mathit{v}\mathit{e}\mathit{c}},{\mathit{p}}_{\mathbf{2}\mathit{v}\mathit{e}\mathit{c}}\right)$ which correspond to the range of $\mathit{e}$ which includes its minimum ($e_{opt}$) + 0.5 deg to obtain ${\mathit{p}}_{opt\_1}$ and ${\mathit{p}}_{opt\_2}$ find the value of $\mathit{e}$ which correspond to the default parameter values to obtain $e_{def}$  end end