Prospects and Constraints of Lowest Astronomical Tide (LAT) as Determination of Sea Boundaries in Indonesia

The determination of the maritime boundary is related to the selection of the tidal datum used in relation to the zero-depth reference. This research was conducted to determine the impact of the zero-depth reference that has been used, the Mean Low Water Spring (MLWS), against the zero-depth recommended by the International Hydrographic Organization (IHO), the Lowest Astronomical Tide (LAT). Tidal data is obtained from BIG's tidal station processing, while the MLWS value data is obtained from a combination of analysis from the Hydrographic Office of Indonesia (Pushidros). Based on these data, it is found that 25 out of 37 tidal stations indicate that the LAT value is below the MLWS in its vertical position. This shows that sea boundary claims can potentially be shifted by changing the zero-depth reference from the original by switching from MLWS to LAT. Lastly, this study presents the benefits of implementing the vertical system reference recommended by the IHO, the LAT, as an international chart datum.