Wave height correction (ISO 15016)

The wave-height correction under ISO 15016:2015 removes the added resistance caused by waves from the measured speed and power so the trial result reports the calm-water performance the contract guarantees. The standard derives the added resistance from the ship’s added-resistance transfer functions obtained by seakeeping model tests, applied to the wave spectrum observed during the run, alongside the parallel corrections for wind, current, water depth, and water temperature and density. Trials are limited to a sea state low enough for the correction to stay reliable, commonly up to about Beaufort 6. The corrected power at the contract speed is what the speed/power acceptance compares against the guarantee.