An Accuracy of Chart Datum in the Tidal Observation Period: Case Study for Teluk Ewa, Pulau Langkawi

This study elaborates the precision of chart datum at Teluk Ewa, Langkawi Island. Observed tidal data for 19 years at Teluk Ewa tidal station were processed and analyzed using the “RMN Asean Australia Tidal Software” to determine values of chart datum for 19 years observation models (Reference datum), yearly, 6 monthly, 3 monthly and monthly. Datum precisions were tested conforming with International Hydrographic Organization (IHO) Standard. IHO had determined that datum error for special class survey must be less than 5cm and 10cm for first class survey and below. Results showed that the standard deviations (one sigma) for all model of chart datum are less than 10cm, however at two sigma it proved otherwise. The trend of chart datum standard deviation indicated that longer period of observation record better standard deviations. Tides are site specific, therefore holistic approach of the country’s chart datum precision could only be modeled once the studies on all tidal stations are completed.