Global Axes
In a 3-Dimensional coordinate system with axes labelled X Y and Z according to the right hand screw system, the bridge deck is defined in the X-Y plane (with Z=0) and the Z direction is vertically upwards. The X direction may also be referred to as 'Easting' and the Y direction as 'Northing'. Vectors can be used to define sub-model planes, and the vectors i j and k are in the directions of X Y and Z respectively.
