Modem computerised navigation systems on board ships require an accurate log for optimal
performance. Traditional electromechanica1logs on board merchant ships have generally been replaced
by Doppler logs, which refer the velocity to the sea-bed. However, their operational depth is limited
and in deep water the velocity is referred to the water-mass some depth below the hull, where it is
influenced by ocean currents. The velocity accuracy ultimately depends on the estimated local sound
The acoustic correlation log has acoustic beams similar to a conventional depth-sounder, with
a vertically downward propagation direction and a broad beamwidth. Compared to the Doppler log it is
affected less by ship pitch and roll due to its broad beamwidth, and the velocity is virtually independent
of the velocity of sound and is referred to the sea-bed to a greater depth.
Temporal correlation logs use a two-hydrophone array and the time delay between the two
received signals is used to calculate the velocity. The full potential of these logs for world-wide ocean
navigation has not been exploited. This thesis investigates the requirements and conditions for temporal
correlation logs on board ships to navigate satisfactorily on and off the continental shelf.
An experimental temporal correlation log working at high-frequencies with continuous wave
propagation is described. It is used to measure the velocity of a tracked platform moving across a water
tank and the results are compared to their theoretical values. When fully developed, the log would be
suitable for shallow-water operation, and techniques learned can be applied to a low-frequency
deep-water correlation log.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.