Yet another mind boggling complication has raised its head!
What reference system should be used for evaluation of the ship equations of motion? Sounds like a fairly simple question - until I started to unpick the various force equations - we have....
1 The Earth coordinate system (x, y, z) easy enough,
2 The ship coordinate system (x, y, z) relative to the centre of gravity of the ship, OK understand that too,
3 The ship coordinate system (x, y, z) relative to the centre of 'floatation' of the ship, bit more mind boggling this one - how do you determine the CoF - complex stuff,
4 The ship rotating coordinate system (yaw, pitch, heave) - phew,
There are probably others but I lost the will to live - translating between this lot has got to cause some problems - carrying on trucking!