ANALYSIS OF GLOBAL TIDE MODEL FOR THE DEVELOPMENT OF LOWEST ASTRONOMICAL TIDES (LAT) MAP OF INDONESIA

• Main Author: Aulia De Silva N., Candida
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/67303
• Institution: Institut Teknologi Bandung

Indonesia is a country that has a very complex tidal phenomenon caused by many small islands, narrow straits, rough seabed, and circulation from the ocean. Currently, there are at least 159 tidal stations throughout Indonesia. Moreover, several areas in Indonesia have very few tidal stations, such as in southern Kalimantan and southern Papua, so tidal characteristics cannot be seen directly in these areas. Lowest Astronomical Tide (LAT) is the lowest predicted state of the tide due to a combination of astronomical conditions over a period of 19 years. Practically, the position of LAT cannot be determined from tidal observations because it takes a very long time. Therefore, to calculate the LAT value by predicting for 19 years through the tidal harmonic constant with at least one year of observation data. However, this method can only be used to calculate the LAT value at one point, namely at the location of the tidal station, so another approach is needed to obtain LAT values throughout Indonesia, one of which is modeling. Currently, there are at least some examples of global tidal models obtained from several methods, including empirical methods using the results of altimetry satellite observations, hydrodynamic modeling methods by performing numerical modeling on certain waters, and assimilation methods by combining results from altimetry satellites, hydrodynamic models and observation at the tide station. This study aims to produce an LAT Map of Indonesia based on the global tidal model and determine the most suitable global tidal model for Indonesian waters. In addition, this research is expected to meet the needs of the LAT Map of Indonesia which can be used for practical purposes in hydrographic surveys and for determining tidal datums for mapping in Indonesia. This study uses at least five tidal models including DTU10, HAMTIDE, FES2014, and TPXO9 v5. From the global tidal model, the amplitude and phase values of the tidal constants are obtained. Based on these data, predictions were made for 19 years using the least square method to obtain the lowest sea level value which was determined as the LAT value. Then a comparison of the LAT value from tidal stations spread over Indonesian waters is carried out with the LAT value generated from the global tidal model. Comparisons were made to determine the deviation value of the global tidal model in all Indonesian waters. In addition, the Root Mean Square Error (RMSE) value was calculated as an approach to determine the most suitable model for use in Indonesian waters. The results of the LAT Map of Indonesia on the DTU10, EOT20, HAMTIDE, FES2014, and TPXO9 v5 models produce maps with relatively the same pattern in the open sea, while in narrow and closed waters they produce different values. This is because the data used to perform tidal analysis in the global tidal model area used both empirical and assimilation methods come from altimetry satellites so the value of the tidal constituent is not as good as in the open sea. In the calculation results, the best RMSE value comes from the tidal model. TPXO9 with a value of 0.078 for other models namely EOT20, FES2014, DTU10, and HAMTIDE respectively have an RMSE value of 0.090; 0.087; 0.090; and 0.095. However, these results can still be said to be comparable considering that the TPXO9 has the highest resolution compared to other tidal models.