Secondary Port

A tidal prediction location whose times and heights are obtained by applying published corrections to a standard port.

Corrections may cover high- and low-water times and heights and can vary between springs and neaps or with the standard port’s predicted values. The exact method is publication-specific and may use interpolation rather than simple constant additions.

Secondary-port results are estimates and can be affected by weather, river flow and local shallow-water effects. The standard port, correction table, time zone, datum and edition must match, and modern official direct predictions should be used when available.