the slant range s to each hydrophone 12 water depth d and the exact location of the interrogation unit 15 the locus of possible positions for each hydrophone may be determined as illustrated in fig3 the vessel 14 moves in a parallel but offset manner to the estimated location for cable 11 preferably one track on each side of the cable thereby establishing a set of loci r 1 r 2 and r 3 for example the intersections of which define the position of each hydrophone 12 in a preferred mode of operation the vessel 14 moves at about one to two knots and the interrogation unit 15 interrogates each hydrophone 12 five to ten times for each of the two parallel offset tracts such hydrophone positions are identified relative to the fixed position of the interrogation unit 15 of the vessel 14 the position of the vessel in terms of latitude and longitude coordinates and hence the interrogation unit 15 is determined by an on board navigational system utilizing satellite navigation monitoring and or radio signals from shore based navigation stations the foregoing described method of the present invention may be repeated any number of times to more precisely define the location of the hydrophones 12 by repeating the described traverses with the vessel 14 the location of each hydrophone is refined to allow for sound refraction effects due to variations in the velocity of sound with water depth in the above described preferred embodiment the vessel navigation system is a miniranger iv radio navigation system the water depth system is a standard.