Surveying by Radio

Radio Record, Volume III, Issue 23, 20 December 1929, Page 15

Surveying by Radio

An Ingenious Method order to determine the exact position, of'a, survey ship during hazy or foggy weather or when the ship is out of sight of land, the American Coastal Survey officials utilise a method called "Radio" Acoustic Ranging." . The purpose of the survey is to chart | the coast lines at regular intervals out to.a-certain depth. . : : In using fhe radio method there -are ’ two shore stations set out by the ship about 35 miles apart. Hach of these is equipped with a radio transmitter, ° receiver and a three-stage bomb audio ‘amplifier, About a thousand yards off shore is a box containing three hydrophones. At a given signal a bomb is dropped overboard from the ship and the exact time and log reading are taken at that-instant. In the ship’s-radid cabin is a chronograph which records seconds with one pen and under-water sounds and radio signals with another pen. As the bomb explodes, the chronograph pen makes a dash on a tape. Seconds are recorded by another pen. After the pomb explodes, the ship operator in. forms the two stations by radio and they switch on their amplifiers in or-> der to receive the sound impulse from the bomb. The amplifiers are used to step up the sound of the bomb réceived by the hydrophones to such a volume as to trip a relay and start an auto-* matie key. The shore operator throws over a switch and three telegraphic dashes are sent back to the ship. Both shore stations must be turned to the same frequency, so that the ship’s receiver can hear them without changing the dial setting. These three radio dashes from each shore station are recorded on the chronograph tape and the exact. time is noted. AS ‘sound travels’. under water with a speed of ‘about 1477 metres per second, the distance to both stations is found ‘and the exact posi-. tion of the ship can be located on the ehart. i *