102 seamanship secrets
date new moon time of tide height of tideA portion of a 2008 tide table for Boston. Th e table provides the time of each high and low
tide for each day of the year and also the height of each tide relative to mean lower low
water (MLLW), which is the vertical datum used by NOAA’s National Ocean Service in its
tide tables (and in the soundings printed on nautical charts). Th e time of low water on the
aft ernoon of August 2 is 1736, which is 1836 Daylight Savings Time. Th e fact that this is a
minus tide (–0.3 feet) suggests that it is a spring tide, and indeed we see that the new moon
was on August 1, so a run of spring tides can be expected.
location time differences,
high and lowreference stationreference stationheight ratios,
high and lowrangesTh is table of diff erences from the National Ocean Service’s 2008 tide tables for the eastern
coasts of North and South America references Neponset, Massachusetts (a subordinate
station), to Boston (a reference station). Times of high and low tides at Neponset are 2 minutes
earlier and 3 minutes, later, respectively, than at Boston, and their heights are 1.0 times the
corresponding heights in Boston—in other words, they’re the same.Another Method to Use Tide Tables