Accurate reconstruction of directional wave spectra is essential for a wide range of oceanographic and engineering applications. Conventional wave data processing methods rely on potential theory, assuming irrotational flow and can account only for vertically uniform currents. These assumptions neglect the effects of ambient vertically shearing currents, which are often present in the ocean. This may lead to inaccurate wave parameter estimations, such as wave heights, periods and direction. This study presents a rotational data processing methodology incorporating the influence of shearing currents by solving the Rayleigh boundary value problem and deriving frequency- and direction-dependent numerical transfer functions. The method was validated through controlled numerical simulations and applied to in situ dataset obtained by an acoustic Doppler current profiler. Simulation results show that the rotational approach substantially improves the accuracy of directional wave spectrum estimations, compared to potential theory methods which were found to overestimate wave height up to 80% and to introduce directional errors exceeding ${10}^{\circ }$, especially when using pressure sensors near the seabed. The study highlights the sensitivity of wave estimates to current shear gradients and underscores the need for robust numerical approaches when interpreting field measurements. These findings have direct implications for coastal engineering, where small directional errors can critically impact sediment transport modeling and infrastructure design.

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• Oceanography
• Shear flows
• Waves and free surface flows