Acoustic techniques for Marine Geodesy

Abstract

Although acoustic transponder navigational techniques have been given growing application in deep sea research over the last ten years, their precision, as normally used, has not improved during that period. It now appears, however, that with careful attention to transponder design, environmental circumstances, and computational methods the present one‐meter uncertainties can be brought down to the centimeter range, making true geodetic application in the seafloor spreading context a feasible prospect. Newly designed echo repeater type transponders with accurately known time delays can provide 10 μ sec or less uncertainty in travel time measurement. Environmental data (primarily near bottom temperature profiles) show that even near spreading centers where hydrothermal activity is expected a properly designed transponder based system, including an instrument to make in situ sound speed measurements to a part in 10⁵, can give the sound velocity information necessary to achieve centimeter precision over the necessary kilometer path lengths.