To derive the residual low frequency current velocity, one usually deploys current meter moorings over 25 hours or more to remove the diurnal and semi-diurnal tidal components.

• 若要得到低频流速（主要是平均流及周期大于一天的海流），通常会施放流速仪，测量海流时间超过25小时，才能将全日潮和半日潮的成分滤除而得低频流的流速。