Use of harmonic consituents in numerical modelling

The tide observed in nature is made up of constituents with periods equal to the periods of the relative astronomical motions of the Earth, Sun and Moon, but with amplitudes and phases which are unique to each location. The tidal prediction printed in tide tables, are derived from a large number of constituents, and the future astronomical positions of the Earth, Sun and Moon. The numerical modeller often requires tides idealised in some manner, and his use differs from that of the hydrographer. This report is a practical guide to the numerical modeller in his special use of these constituents.