A sandstone bed strikes 067 and dips 21 degrees SE. In the bedding plane we find ripple marks pitching 58 degrees east. What is their trend and plunge? Pitch is the angle between a line in a plane and the horizontal, measured in the plane. Thus, this problem is nothing more than measuring off an angle on a great circle (the bedding plane).
1. Plot the strike of the plane. Draw a small symbol to indicate the dip direction and the pitch of the line.
2. Rotate the overlay to bring the strike to the north-south axis, and plot the great circle representing the plane.
3. Count off the pitch from the appropriate end of the great circle. The sketch symbol you drew in step 1 will show which end to start from.
4. Find the trend and plunge of the plotted line.