Deriving offshore tidal datums using satellite altimetry around Malaysian seas

Abstract

Tidal datums are important for calculating spatial coordinates especially the elevation relative to mean sea level and also crucial for defining the state sovereignty boundaries over maritime areas. Normally, sea level was measured by tide gauges along the coastal for tidal datums computation. However, knowledge of tides is still restricted in coastal areas. Furthermore, tidal range at offshore was simply assumed to be similar as coastal due to the difficulties installing offshore tide gauges. The launching of satellite altimeter technologies with precise orbit determination since 1993 had provided significant accuracy of sea surface height (SSH) measurements. The observed SSH from satellite altimetry can be offered as tide gauge measurements at each location globally. This study aims to derive offshore tidal datums using satellite altimetry around Malaysian seas. SSH time series from TOPEX, Jason-1, Jason-2 and Geosat Follow On (GFO) were analysed using harmonic analysis approach to estimate harmonic constants. A minimum of 19 years tidal predictions were then performed using UTide software to determine Lowest Astronomical Tide (LAT) and Highest Astronomical Tide (HAT). These tidal datums were interpolated into regular 0.125° grids and were assessed with ten selected coastal tide gauges. The findings showed the Root Mean Square Error (RMSE) of spline interpolation yielded better accuracy, 25.5 cm (LATMSL) and 17.4 cm (HATMSL) as compared to the RMSE of Kriging interpolation, 31.8 cm (LATMSL) and 33.8 cm (HATMSL). In conclusion, deriving offshore tidal datums can serve as input data to unify marine database with coastal areas and also can support many marine applications.

Quasi-Continuous Tidal Datum for Peninsular Malaysia using Tide Gauge, Satellite Altimetry, and Tide Model Driver (TMD) Data

“…The tide gauge data of 12 stations in Peninsular Malaysia were considered over a duration of 23 years, from 1993 to 2015. According to [8,[21][22], the minimum period of tidal observation for a stable tidal datum determination is 18.6 years, which represents the time spent by the moon to make a complete revolution around the Earth. Therefore, since this study uses 23 years of tidal observation data for tide gauge, satellite altimetry, and TMD, it complies with the aforementioned requirement.…”

“…The non-sun synchronous satellite mission was chosen in this study due to its compatibility with harmonic analysis. For this study, since it shares a similar orbit, the TOPEX class satellite mission (TOPEX, Jason-1, and Jason-2) was combined to create a single time series data encompassing 23 years of tidal observation from 1993 to 2015 [8,9]. Equivalently to the tide gauge data, the combination of the TOPEX class mission also complies with the requirement of 18.6 years of tidal observation for a stable tidal datum determination.…”

“…Equivalently to the tide gauge data, the combination of the TOPEX class mission also complies with the requirement of 18.6 years of tidal observation for a stable tidal datum determination. On the other hand, due to its different orbit from the TOPEX class satellite mission, the GFO satellite mission cannot be combined with the TOPEX class mission [7][8][9]. However, owing to its compatibility with harmonic analysis, the GFO mission was also utilized as an additional satellite altimetry data to ensure denser data coverage for the tidal datum determination.…”

“…The satellite altimeter has been evolving since 1975. Currently, there are a total of 13 satellite missions that have been operating from 1985 to 2022, such as TOPEX/Poseidon, Jason-1, Jason-2, Jason-3, GEOSAT Follow On (GFO), ERS-1, ERS-2, ENVISAT-1, Cryosat-2, SARAL, and Sentinel-3A and Sentinel-6 [7,8]. Accordingly, a satellite altimeter has three long-term scientific objectives, which are observing the circulation of the oceans, monitoring the volume of the polar ice plate, and observing the variation in the sea level.…”

Interpretation of Current and Tidal Pattern at Selangor River, Kuala Selangor

“…The M2 component is the most important lunar component and is linked to the Moon's direct gravitational influence on the tides. Similarly, the S2 constituent is the most significant solar ingredient and is associated with the Sun's direct gravitational influence on the tides (Hamden et al, 2021). These tidal signals have two peaks every 24 hours.…”