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# Sign Convention

## XYZ Convention

The following convention is used for the XYZ axes of RocSlope models:

• X-axis and Y-axis make up the horizontal plane.
• Positive Y-axis is north and positive X-axis is east.
• Z-axis is always the vertical axis and is positive upwards.
• Rotation follows the right-hand rule where the thumb is pointing in the positive direction along the axis of rotation and the curled fingers indicate the positive rotation direction. This applies to all input angles in the program except for bearing angles for Dip and Dip Direction, and Trend and Plunge. See below for more information.

## Dip and Dip Direction

The Dip and Dip Direction are used to describe the inclination and direction of the steepest angle of descent for planar structures in RocSlope (e.g., joint orientation). The Dip Direction is the rotation angle about the vertical Z-axis measured from the Y-axis (north). Positive is taken as rotating clockwise from the Y-axis (north) towards the X-axis (east). Dip is the rotation angle downwards from the horizontal XY plane after the Dip Direction angle is applied.

## Trend and Plunge

The Trend and Plunge are used to describe the orientation of vectors in RocSlope (e.g., line of intersection, load direction, sliding direction). The Trend is the rotation angle about the vertical Z-axis measured from the Y-axis (north). Positive is taken as rotating clockwise from the Y-axis (north) towards the X-axis (east). Plunge is the rotation angle downwards from the horizontal XY plane after the Trend angle is applied.