00:00 is midnight, 06:00 is 6am, 12:00 is noon and 18:00 is 6pm. Sea Level Observed sea levels are in metres above Tide Gauge Zero (e.g. 1.205 metres) AHD Australian Height Datum in metres above tide ...
The earth monitoring installations provide Global Navigation Satellite System (GNSS) measurements to allow absolute determination of the vertical height of the tide gauges that measure sea level.