Determination of wave direction using an orbital following buoy

Abstract

Software has been developed in FORTRAN language using a personal computer for the determination of wave direction from time series measurements of heave, pitch and roll of an orbital following buoy. The method of digital band pass filtering describEd. by Edward C. Brainard 2 of Endeo Inc., USA was used. A derivation of the basic formula used is presented. The software developEd. by us, viz. BUOY-D-P.FOR, and the software providEd. by ENDECO, viz. 1156DBP. EXE, were both run for observed as well as computed simulated data. This is a preliminary report on program development. In the case of observed data, wave directions obtained with BUOY-D-P agreed within within plus or minus 5 degrees with the single available visual estimate of swell direction and within plus or minus 50 degrees with directions obtained with 1156DBP. In the case of computer simulated data, BUOY-D-P was able to recover wave directions accurately for both mono-chromatic and multi-chromatic wave trains. 1156DBP was equally successful, except that if the simulated wave direction was theta, the computed direction was found to be mu + theta. This offset has been explained.