Chapter 2 – Terminology

It should be noted that, while the terms listed below are in common usage, they are not those given in MSC/Circ.920, MODEL LOADING AND STABILITY MANUAL, section 2.2, table 1, which are based on ISO standards (ISO 7462 and ISO 7463).

Particular care should be taken with regard to asymmetric weight and buoyancy distribution.

Term, as used in the 2008 IS Code	Term, as used in MSC/Circ.920	Explanation
LCG	XG	Longitudinal Centre of Gravity (m from A.P.)
		Longitudinal distance from reference point to centre of gravity, reference point usually at Aft Perpendicular (forward + / aft -).
TCG	YG	Transversal Centre of Gravity (m from C.L.)
		Transversal distance from reference point to centre of gravity, reference point on the Centreline (port + / starboard -).
VCG	KG	Vertical Centre of Gravity (m above B.L.)
		Vertical distance from reference point to centre of gravity, reference point on Base Line (upwards + / down -).
LCB	XB	Longitudinal Centre of Buoyancy (m from A.P.)
		Longitudinal distance from reference point to centre of buoyancy, reference point usually at Aft Perpendicular (forward + / aft -).
TCB	– –	Transversal Centre of Buoyancy (m from C.L.)
		Transversal distance from reference point to centre of buoyancy, reference point on the Centreline (port + / starboard -).
VCB	– –	Vertical Centre of Buoyancy (m above B.L.)
		Vertical distance from reference point to centre of buoyancy, reference point on Base Line (upward + / down -).
LCF	XF	Longitudinal Centre of Flotation (m from A.P.)
		Longitudinal distance from reference point to centre of flotation, reference point usually at Aft Perpendicular (forward + / aft -).
TCF	– –	Transversal Centre of Flotation (m from C.L.)
		Transversal distance from reference point to centre of flotation, reference point on the Centreline (port + / starboard -).

In all cases it is of utmost importance to define clearly the reference points/planes and the signs of the positive and negative directions along the vessel’s coordinate system.