Standard Port Tidal Levels
Tidal levels table
For help understanding column headings used in this table see Definitions of Tidal Terms.
- The above levels, in metres, are referred to Chart Datum, which is the same as the zero of the tidal predictions in all cases.
- The values for the MHWS, MHWN, MLWN and MLWS tidal levels given in the table are the averages of the levels of all spring and neap tides predicted for the period 1 July 2012 - 30 June 2013 using the harmonic constituents derived from the analysis of the observations made at that port during the period given on the Standard Port Periods of Observation page. The average annual value of MHWS etc. varies from year to year in a cycle of approximately 19 years. This variation is in the order of up to 0.1 - 0.15 metres.
- The values for the spring and neap ranges have been deduced from the spring and neap tidal level values. As a consequence of the annual variation of the tidal levels, the variation in the ranges of the spring and neap tides over the 19 year cycle is twice that of the levels.
- The value of MSL for each port has been derived from the analysis of tidal observations made at the port during the period given in the table on the Standard Port Periods of Observation page.
- The values for HAT and LAT given in the table above are the highest and lowest tidal levels that are predicted to occur under average meteorological conditions during the period 1 January 2000 - 31 December 2018 using the harmonic constituents derived from the analysis of the observations made at that port during the period given in the table on the Standard Port Periods of Observation page.
- This table is not intended to be used for the determination of cadastral or administrative boundaries. A table of standard port values for cadastral purposes is available on this website.