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Astronomical tide is often imported once a year into the system as an external historical, even though it's in fact a forecast. Default the WaterCoach mode won't show future values of external historical timeseries. To be able to show the tide "forecast", an exception has been made for external historical timeseries with synchlevel=4. This same synchlevel also for proper synchronisation of this data to the OC in a live system (see B Enumerations#A.5SynchronisationLevels). Note that the synchLevel=4 should explicitly be specified also in the display configuration files (e.g. Filter.xml, etc) in order for the future values of the timeseries to be visible in WaterCoach.
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