The UK Hydrographic Office has copyright over the harmonic constant tables used to calculate accurate Tide times and tide heights around the U.K. A licence has to be purchased to use these tables.
An alternative less accurate method uses the interaction of planetary
bodies, namely the Moon and Sun.
The phase of the moon can easily be calculated and by knowing the actual time of day of the moons phases throughout the year
plus past high tides, then an estimate can be made of tides in the future. However, the necessary calculations are taking too long.
Hence , as a start, the program normally used to calculate tides using harmonic constants was amended to delete all the UKHO harmonic constants
and then add a single normalised constant. This was adjusted by trial and error to give symmetrical errors throuhout the year. 90% of the tides
so calculated lie within one hour and 99% within one hour and a half of the actual historic tides.
If you have any comments or suggestions on the tide tables then please EMail me