Table 6.

Pre-calibration, root mean square error (RMSE), mean absolute error (MAE), and mean percentage error (MPE) calculated from the comparison of measured tilt angles $D_{\mathrm{i}}$, and reference tilt angles ($\mathit{WRef}$) in $X$- and $Y$-direction. Polynomial fit equations (forced through zero), coefficient of determination ($R^2$), $\mathit{RMSE}$, $\mathit{MAE}$, and $\mathit{MPE}$ calculated from the comparison of calibrated tilt angles (${\mathit{WM}}_{\mathrm{d}}$), and $\mathit{WRef}$.

	Pre-calibration			Post-calibration
Axis	$\mathit{RMSE}$(°)	$\mathit{MAE}$(°)	$\mathit{MPE}$(%)	Polynomial fit	R2	$\mathit{RMSE}$(°)	$\mathit{MAE}$(°)	$\mathit{MPE}$(%)
+$X$	0.281	0.281	3.204	$0.0008\bullet D_{\mathrm{i}}^2+0.9618\bullet D_{\mathrm{i}}$	1.000	0.006	0.017	0.191
−$X$	0.093	0.097	−0.829	$0.0006\bullet D_{\mathrm{i}}^2+0.9988\bullet D_{\mathrm{i}}$	1.000	0.005	0.011	−0.116
+$Y$	0.157	0.159	1.904	$0.0004\bullet D_{\mathrm{i}}^2+0.9789\bullet D_{\mathrm{i}}$	1.000	0.001	0.017	0.208
−$Y$	0.091	0.095	−0.749	$0.0006\bullet D_{\mathrm{i}}^2+0.9989\bullet D_{\mathrm{i}}$	1.000	0.006	0.011	−0.076