ABSTRACT Based on the results of the analysis and discussion in this study, the following conclusions can be drawn, on indirect tidal data for 29 days in the waters of Rupat Strait processed using the Admiralty method, the value of the chart datum model is MSL 0.076m, HHWL 163.411m and LLWL -163.259m. The relationship between the chart datum obtained with bathymetry data, that the Z0 and MSL v…