OPTICAL MEASUREMENTS OF CAPILLARY-GRAVITY WAVE SPECTRA USING A SCANNING LASER SLOPE GAUGE

A description of a new scanning laser slope gauge (SLSG) is given and the results obtained from both laboratory wind-wave tank and field mea surements are presented. The device relies on the measurements of two components of surface slope to compute spatial and temporal lags that are used to estimate the full three-dimensional slope spectrum. The de vice is capable of resolving frequencies up to 34.7 Hz and wavelengths in the range between 7.9 X 10(-3) and 3.08 X 10(-1) m. The technique makes use of a two-dimensional laser scanner that samples the perimete r of a circle of 0.154-m diameter (an unfilled aperture). Both laborat ory and field results indicate the device is well suited to measure th e full three-dimensional spectra of capillary-gravity waves and is cap able of providing ground-truthing measurements for the verification of remotely sensed ocean surface features.