AID TO SHIPPING.

Taihape Daily Times, Volume XI, Issue 3372, 29 December 1919, Page 7

AID TO SHIPPING.

SOUNDS UNDER VVATER.

An intereting new me’fhod—known as sub~aqueous sound ranging—of determining the position of a ship at sea. is explained in a .s.tatem_ent issued by the ‘Admiralty. The system, is pointed out, has been of great value for war operations, and will, if de—veloped, be of great benefit to shipping under peace conditions. '

From a broad outline of the method, it appears that four or five hydrophones are established under water. at distances apart of about five miles, each one being connected by cable to a recordingstation on shore_ A. sec-i ond recording station is established at ~ any suita'b-le distance, these two sta-i tions forming the extremities of a. base i of known length and bearing. Anyl ship within the working limits of these two stations, and well situatedl in respect to the base line, can have her position exactly determined by causing a subaqueoug explosion, such as dropping a depth charge. The position is obtained by photographieally recording ‘and measuring at each station the differences of time of the receipt of the sound of the explosion at the hydrophones. A vessel employing this method must be fitted with wireless telegraphic apparatus, arranging beforehand for the receipt of the sound. of the explosion, and ‘transmission of the sulbscquent inforllllatloll, from the Control a recording istation. A vessel approaching a port in :1 fog,'it is stated, could rely on a series of positions by sound I'-auging and reconcile them with her movements in the intervals between them. ' During the war niinefields were laid and bombarding positions for ships out of sight of land were found with the greatest precision; explosions in minefields were recorded and their positions? accurately fixed, enabling paitrols to proceed to the spot to eluci|date the cause.

Sound ranging stations are at pre—sent. established at St: Margaret ’s Bay (near Dover), Easton Broad (near Lotwestoft), Flamborough Head, Peterhead, and Lerwick. The three last. are, however, being closed in the interests of economy.

Shipping companies and others interested with a View to adopting :th‘is method are invited to communicate with the Admiralty by letter in the first instance. Actual trials lnay possibly be arra.ngcfl. “The method,” it is observed, “is at present only_in its infancy, and cannot"be said to. be at present suitable for c'ommere.ia.l use.‘ It is, of course, capable of great development, and it will probably be found that only very small explosive charges are required to give the records. ‘