COMPASS ADJUSTMENT.

New Zealand Herald, Volume LXII, Issue 19050, 22 June 1925, Page 10

COMPASS ADJUSTMENT.

RADIO DIRECTION-FINDING. AORANGI'S TESTS IN GULF. The Aorangi, which arrived at Auckland from Vancouver yesterday, anchored in the Hauraki Gulf for over two hours to check the error of her wifeless direc-tion-finding compass. The vessel anchored at about noon in a position midway between Jin Island and I?Ungitoto Beacon. Her launch, which is fitted with wireless, was then lowered into the water and was sent away about a mile and a-half. Keeping that distance the launch circled slowly round the Aorangi and reciprocal bearings were then taken. The correct bearing of the launch on each point of the compass was noted by the master and officers on the Aorangi's bridge, and at the same time bearings of wireless signals from the launch were noted by the Aorarigi's operators by means of the /wireless compass. The angle between the correct bridge compass bearing and the wireless bearing showed the margin of error. *' Mariners' ordinary compasses are tested in a somewhat similar manner, but the vessel is generally swung round on a pivot and the bearings of a distant object are checked on every point of the compass. With the ordinary ship's compass the errors are caused either by magnetism in the iron included in the vessel's structure or by the earth's magnetism. These errors can be counteracted to a large extent by placing permanent magnets near the compass. The error of the wireless compass is not caused by magnetism, but by the wireless waves being retracted by the metal hull of the vessel. These errors of the wireless compass cannot be. adjusted, but when they are known they can be allowed for when the wireless compass is being used for direction-finding purposes. While the Aorangi was anchored in the gulf she was medically examined and cleared, by the customs. Consequently, when she came into port after three o'clock she berthed at the Queen's Wharf without anchoring again.