Projections. Attempts to delineate some part of curved surface of Earth on the flat surface of a map or chart. It is impossible to do this with accuracy. In the projections used by seamen the distortions are either negligible in practice or are of a known nature and value and can, therefore, be allowed for. The different projections are treated under their separate names. Prolate Spheroid. Spheroid generated by semi-rotation of an ellipse around its major axis. Sometimes applied to a spheroid that rotates on its major axis.