Two practical techniques of correction methodand fitting method for computing major diurnal and semidiurnaltidal currents from irregular satellite-tracked drifter position data havebeen developed and then applied to the Yellow and East China Seas to computeM2 and K1 currents. The correction methodcalculates the most dominant diurnal and semidiurnal tidal currents usingthe correction coefficients, defined amplitude ratios, and phase differencesbetween the major tidal currents. On the other hand, the fitting method calculatesmajor tidal currents by fitting the amplitudes and phases to a given polynomialfunction in space, without utilization of the correction coefficients. Validationtests for sampling intervals, data truncation, effects of low-frequency currents,and position errors are performed to improve computation results. Both methodsenable us to evaluate effectively and correctly strong tidal currents providedthat the signal-to-noise level in drifter positions is not significantly high.The spatial pattern and current ellipses of M2 and K1tidal currents from drifter positions in the Yellow Sea are fairly well consistentwith those from moored current data. Application of the two methods to theYellow and East China Seas exhibits commonly that M2 andK1 currents rotate clockwise in the East China Sea but counterclockwisein the Yellow Sea interior, with rotation direction change around 35¿and 34¿ N, respectively.