I think the only point really being made is dependant on size, what point of a possibly HUGE platform is your MAPt based on. If it is the centre of the structure then you will have the same distance from all four points of the compass, if the heli deck then that will be a different distance from the structure depending which way the pad sticks out. A smaller platform like some in GOM and southern north sea will be less of a problem but the larger one's will need to be considered carefully. Like HC has said the Ekofisk is HUUUGE and where is your datumn point on that monstrosity?
Si