Definition

The interval of time between the TRANSIT (upper or lower) of the MOON over the LOCAL or GREENWICH MERIDIAN and the next HIGH WATER or LOW WATER at a place. The interval is assumed to be local unless otherwise specified. The average of all high water intervals is called mean high water lunitidal interval, high water interval, or corrected establishment. The average of all low water intervals is called mean low water lunitidal interval, or low water interval. The expressions higher high water interval, lower high water interval, higher low water interval, and lower low water interval are used when there is considerable DIURNAL INEQUALITY. See ESTABLISH­MENT.