Specifies the roll angle for the object. The Roll angle measures between the local z-axis of the object and the Z-axis of the global coordinate in the YZ-plane. Another way to describe roll is the rotation of the object about its x-axis. This option sets the reference in the model to a line that is perpendicular to the local coordinate system x-axis and in the horizontal plane. Roll angles are measured clockwise from horizontal to the y-axis of the local coordinate system. The roll angle is between 0 and 360 degrees. You can enter negative roll angles, but the software automatically converts them to the positive equivalents. If the pitch is set to +/- 90 degrees, then the reference in the model is the North axis.