Two sets of axes are used in the Aqwa suite; these are shown in Figure 1.1: Axes Systems. They are the FRA (Fixed Reference Axes) and the LSA (Local Set of Axes).
Fixed Reference Axes (FRA): X,Y,Z in the free-surface with Z pointing vertically
This is also known as the Global Axis Systerm. This system has its origin on the mean water surface with Z axis pointing upwards, X and Y on the mean water surface. The mean water surface is at Z=0. This axis system will not move at any stage of the Aqwa analysis.
Local System Axes (LSA): x,y,z with origin through the body's center of gravity
The Local System Axis (LSA) has its origin at the CoG of the vessel, with X, Y and Z axes parallel to the FRA (see 1 above) when the vessel is in its initial definition position. With conventional modelling, X is along the length of the vessel, Y along the beam to port, and Z in the direction of the cross product of X and Y. This axis system moves with the vessel.
