It may be useful at the end of this symposium to ask broadly what has been achieved so far in the field of navigational radar and what are the outstanding problems.

In this country alone, in the four years since the end of the war, rather more than 300 commercial radars have been manufactured to an exacting specification and fitted to merchant vessels, and a much larger number has been produced in the United States; during 1949 the British radar industry states that it hopes to fit more than a ship a day.