Time of flight measuring system for lakes acoustic tomography

Acoustic scalar and vector tomography appears as a promising technique for monitoring the distribution of temperature and water mass velocity in lake basins. This paper, after a brief description of the algorithm for the tomographic inversion, and the required specifications for the time of flight measuring system, describes the architecture of a synchronisation and data acquisition station realised for the LAT (lake acoustic tomography) feasibility study. The aim of this apparatus is to generate two synchronous triggers for the acoustic signal transmission from two hydrophones placed several kilometres apart. The same systems also generate the acquisition triggers for data recording of the two received acoustic pulses. Subsequent signal processing of the recorded data allows the estimation of the time of flight in the two directions and its variation.