Radio acoustic ranging

At the distances involved – generally less than 200 nautical miles (370 km) – each of these radio signals arrived at the ship at essentially the same instant that each of the remote hydrophones detected the sound of the explosion.

[1] The sinking of RMS Titanic in 1912 due to a collision with an iceberg spurred the Canadian inventor Reginald Fessenden (1866–1932) to begin work on a long-distance underwater sound transmission and reception system that could detect hazards in the path of a ship.

Nicholas H. Heck (1882–1953), a Coast and Geodetic Survey Corps officer, had been assigned from 1917 to 1919 to World War I service with the United States Naval Reserve Force, during which he had researched the use of underwater acoustics in antisubmarine warfare.

Heck agreed, but believed that existing navigation aids would not meet the needs of the Coast and Geodetic Survey in terms of the immediacy and accuracy of position fixes.

[4][5] Heck oversaw tests at Coast and Geodetic Survey headquarters in Washington, D.C., that demonstrated that shipboard recording of the time of an explosion could be performed accurately enough for his concept to work.

[4] He worked with Dr. E. A. Eckhardt, a physicist, and M. Keiser, an electrical engineer, of the National Bureau of Standards to develop a hydrophone system that could automatically send a radio signal when it detected the sound of an underwater explosion.

Under his direction, Guide both tested her new echo sounder's ability to make accurate depth soundings and conducted radio acoustic ranging experiments in cooperation with the U.S. Army Coast Artillery Corps.

[4] In late November 1923, with Heck aboard, Guide began a voyage from New London via Puerto Rico and the Panama Canal to San Diego, California, where she would be based in the future, with her route planned to take her over a wide variety of ocean depths so that she could continue to test her echo sounder.

[4] Before she reached San Diego in December 1923, she had accumulated much data beneficial to the study of the movement of sound waves through water and measuring their velocity under varying conditions of salinity, density, and temperature, information essential both to depth-finding and radio acoustic ranging.

[4] Under Heck's direction, Guide then conducted experiments off the coast of California during the early months of 1924 that demonstrated that accurate echo sounding was possible using the new formulas.

Local peculiarities in the propagation of acoustic waves in the water column could degrade its accuracy, there were problems with maintaining hydrophone stations, and handling explosive charges posed a considerable danger to personnel and ships.

However, World War II, which by then had been raging for three years, gave impetus to the rapid development of purely radio-based navigation systems to assist bombers in finding their targets in darkness and bad weather.

Radio acoustic ranging appears not to have been used after 1944,[1] and by 1946, Coast and Geodetic Survey ships had switched over to the new SHORAN electronic navigation technology to fix their positions.

Nicholas Heck revolutionized oceanic surveying through the use of radio electronic ranging to establish ship locations, one of his major contributions to oceanography.

A 1931 U.S. Coast and Geodetic survey illustration of radio acoustic ranging using anchored station ships.
A U.S. Coast and Geodetic Survey radio acoustic ranging station on California ′s San Clemente Island in 1925, when it supported hydrographic survey operations by the survey ship USC&GS Guide .
A U.S. Coast and Geodetic survey illustration of radio acoustic ranging and echosounding techniques used in combination.
A U.S. Coast and Geodetic Survey radioman on duty at radio acoustic ranging station KGHS, Kodiak Island , Territory of Alaska , supporting hydrographic survey operations by the survey ship USC&GS Surveyor in 1929.
Nicholas H. Heck, photographed ca. 1940.
USC&GS Guide was a survey ship in commission in the U.S. Coast and Geodetic Survey fleet from 1923 to 1941. She was the first ship to employ radio acoustic ranging operationally.
The U.S. Coast and Geodetic Survey launch USC&GS Helianthus , which operated from 1919 to 1939, mostly in the waters of the Territory of Alaska . She is equipped with an antenna wire for radio acoustic ranging operations.
A U.S. Coast and Geodetic Survey illustration of a "radio-sonobuoy" in operation.
A U.S. Coast and Geodetic Survey officer aboard a survey ship prepares a bomb for use in radio acoustic ranging during hydrographic survey operations.
A 1936 U.S. Coast and Geodetic Survey illustration of a "radio-sonobuoy." The buoys entered service in July of that year.
The U.S. Coast and Geodetic Survey launch USC&GS Pratt putting to sea to serve as a hydrophone station ship for the survey ship USC&GS Hydrographer during radio acoustic ranging operations in the Gulf of Mexico sometime between 1933 and 1937. She flies the United States Coast and Geodetic Survey flag from her mast and the national ensign at her stern.