Historical Predictions and Datums A set of tidal harmonic constants based on data collected prior to 1960 have been calculated for use in generating tide predictions at this location. Due to the limitations of these historical observations, MSL is held fixed as the station datum and MLLW is referenced to MSL in order to remove any reference to the terrestrial system. The removal of the terrestrial reference enables the relationship between MSL and MLLW to remain consistent over time and not require periodic National Tidal Datum Epoch (NTDE) updates. Due to the remote nature of this location, there are no immediate plans to collect updated water levels data in the area. If you require additional assistance, please contact CO-PS Customer Service via email at Tide.Predictions@noaa.gov.