On the variation of LAT resulting from predictions computed using different tidal constituent sets

Hsien Kuo Chang, Ching Chung Cheng, Peter Tian Yuan Shih*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


While the Lowest Astronomical Tide (LAT) has a clear definition as the lowest water level caused by astronomical attractions at a water level station, there are variations in the implementation schemes for practically deriving LAT from a time series of tides. This article explores the variation resulting from different tide constituent sets, as named by the numbers, 25, 37, or 60 constituents. Hourly observations of 34 stations around Taiwan were examined in this study. Using LAT-60, the LAT with 60 constituents, as the reference, when the nodal correction is applied, the average deviation of LAT-25 is −2.12 cm, LAT-37 is 0.70 cm, and ISLW is 22.44 cm. Based on the experiments conducted, it is found that the difference between LAT-25 and LAT-60 is 1.18 cm as measured by the third quartile without nodal correction, and 0.89 cm with nodal correction. Nodal correction will lower the water level about 2 cm on average and maximum about 6.7 cm. ISLW is higher and has less influence by nodal correction than LAT so it is difficult to be regarded as a fairly stable water level for chart datum.

Original languageEnglish
Pages (from-to)31-38
Number of pages8
JournalJournal of the Chinese Institute of Engineers, Transactions of the Chinese Institute of Engineers,Series A
Issue number1
StatePublished - 2023


  • harmonic analysis
  • Indian spring low water
  • Lowest astronomical tide
  • nodal correction
  • Ou
  • Ou
  • Yu-Chen
  • Yu-Chen


Dive into the research topics of 'On the variation of LAT resulting from predictions computed using different tidal constituent sets'. Together they form a unique fingerprint.

Cite this