The problem of navigating a vessel under conditions of bad visibility in open sea and in coastal waters has in recent times been largely solved by the advent of modern aids. The problem in pilotage waters, however, still remains severe and the handling of a sizeable ship in estuaries and harbours in bad visibility is today the exception rather than the rule.

The lack of progress in this field is due mainly to two causes. The first of these causes is the lack of a clear understanding of the pilotage requirements; the discussion at this meeting may help to shed some light on this problem. The second is referred to later. Commander Akerman has stated some of the pilot's requirements and the object of the present paper is to illustrate and further clarify the problem by examining some of the possible systems available to aid its solution. The paper will concentrate on radio systems since these seem the ones most likely to aid in solving the bad-visibility problem.