Investigation of variations of long surface wave parameters by optical techniques during JUSREX 1992

For investigation of long surface waves a passive optical device for construction of space-time images of the sea surface using optical profiles obtained from the bow of a ship was developed during the JUSREX 1992. The optical method for ship motion compensation using the jump of brightness on the horizon was developed. The perspective distortions of the optical image was eliminated using averaging of the sea profiles by a slide window method. The imaging accuracy is given. Two space-time images of the sea surface were obtained from two optical devices with different directions of observations. Two such space-time images allows the determination of the the kinematic characteristics of long surface waves. Software was developed for representing these images on a TV monitor in real time. The geometrg of observations is presented on the lower part of the picture. One can see on the picture the images of swells and long wind waves as the dark and bright stripes. The analysis of these images allows determination of swell period.