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lunitidal interval |
the interval between the moon's transit
(upper or lower) over the local or Greenwich meridian and the following
high or low water.
The average of all high water intervals for all phases of the moon is
known as mean high water lunitidal interval and is abbreviated to high
water interval. Similarly the mean low water lunitidal interval is abbreviated
to low water interval. The interval is described as local or Greenwich
according to whether the reference is to the transit over the local or
Greenwich meridian. When not otherwise specified, the reference is assumed
to be local. When there is considerable diurnal inequality in the tide
separate intervals may be obtained for the higher high waters, the lower
high waters, the higher low waters and the lower low waters. These are
designated respectively as higher high water interval, lower high water
interval higher low water interval, and lower low water interval. In such
cases, and also when the tide is diurnal, it is necessary to distinguish
between the upper and lower transit of the moon with reference to its
declination.:: |
