In this paper we shall seek to discover what information we need in order to navigate and how this information is obtained. To do this we first define what we are talking about and then, by a logical process, determine the components involved and the ways they can be measured. Efforts to discover whether another science has been approached in this basic way have failed. All that can be said with certainty is that the path is fraught with difficulties.

The word navigation has nautical origins but the scope of the discipline is far wider today. Nevertheless, a modern definition must stem naturally from marine operations. There would seem to be four factors:

(a) A ship at sea is not navigating when she is docked. There has to be motion.

(b) Rocking to and fro is not enough. The motion has to be from one place to another.

(c) Drifting helplessly before the wind is not being navigated. The motion has to be under control.

(d) The word ‘control’ has a negative and restricting connotation whereas travel has positive aims. Hence the control has to be exercised to a purpose. Steering aimlessly, however complete the control, is not navigating.

A definition of navigation should therefore include four features, motion, place, control and purpose. A possible wording might be:

‘Navigation is purposeful control of motion from place to place’.