These options are used in calculating gauge face angle.
If gauge face wear on a profile does not exceed Minimum Wear, gauge face angle is not calculated. In this case it is set to 0.0.
Reference Distance is the distance below track level of the gauge-face angle reference point. It is often set to the same value as the gauge point reference distance.
Below Reference and Above Reference are distances below and above the gauge face angle reference point that are taken into account when calculating gauge face angle. Re-sampled points in this region are fitted to a straight line. Gauge face angle is the angle between the fitted line and a vertical defined with reference to track level.
Minimum Coverage is the minimum percentage of the defined region of interest where data must exist for calculating gauge face angle. Coverage is 100% if there are no gaps in the defined region of the gauge face. If coverage drops below the minimum setting, gauge face angle will not be calculated.
If a more sophisticated gauge face angle calculation is required, a customized gauge face angle macro may be used. In that case, the Gauge Face Angle options in this dialog work in combination with the macro.