A.reduce the variation as much as possible B.reduce the deviation as much as possible C.reduce the magnetic dip as much as possible D.allow the compass bowl to swing freely on its gimbals
A.a collision with another vessel B.being moored on a constant heading for a long period of time C.being struck by lightning D.All of the above
A.being moored for a long time on one heading B.being struck by lighting C.steaming from the north magnetic hemisphere to the south magnetic hemisphere D.loading a homogenous magnetic cargo such as steel plate,iron bars,etc