Select this parameter to compute the angle of line and curve features to the horizontal. In case of a curve feature the angle is measured for the straight segment connecting the endpoints of the curve.
The direction of angle measurements depends on the Y-axis direction in the image calibration scale. If the Y-axis is pointed down (which is a default setting), the angles are measured form the positive X-axis clockwise. To measure the angles counterclockwise, reverse the direction of Y-axis. See Spatial Calibration for more details.