I've noticed major discrepancies between the times windy predicts for slack and the iOS Current Atlas app. Which is the better of the two to rely on and why? I'm just learning this stuff and read the recent "Slack Times" thread with interest.
My understanding of the "why" part is that the tide and current tables are derived from measurements so based historical data that are very specific to the station. Overall the tides (and hence tidal currents) are related to the relative motions of the Earth, Moon and Sun (see tidal theory) so are periodic on a variety of timescales (Metonic Cycle). Many apps and other compressed data sources base the values they report on periodic harmonic models of varying complexity- less data needs to be stored, then the values are computed. These can be in error due to the sophistication of the calculation, the input data (the model parameters for each station), and then due to local effects that are hard to capture in these general models.Which is the better of the two to rely on and why?
Did you even read my post ??nootka, the computer code itself is exact. It will run the same calculation steps every time. It’s the quality of the input data to formulas that is variable.