Mean high water is the average height of the high tides over a 19-year period.
According to the reference provided, mean high water is determined by averaging high tide heights. However, the duration of the observation period matters.
- Long-term Measurement: Ideally, the average is calculated using high tide data collected over a complete 19-year period. This extensive timeframe helps account for cyclical variations in tides.
- Short-term Measurement: If data is collected for a period shorter than 19 years, corrections are applied. These adjustments eliminate known variations, effectively scaling the short-term data to be equivalent to a 19-year mean high water value.