You have your global XYZ directions, which you can visualize with the CAESAR II graphics (look at the compass in the lower left hand corner). Direction cosines line up with this axis system:

( X, Y, Z )
( 1, 0, 0 ) is horizontal in the X direction
( 0, 1, 0 ) is vertical in the Y direction
( 0, 0, 1 ) is horizontal in the Z direction