We have the tide on the GPS, but I think the chart would be easier to use and it doesn't require batteries
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I'm sure you're aware of the difference between tides and currents. And not the just basic definition of height vs horizontal speed.
What I am referring to is the TIME DIFFERENCE between tides & currents. Max and min currents can runs hours before or after highest and lowest tides.
Relying on your GPS tide information for currents could make you miss a max or slack current,
big time. That's why NOAA publishes both tide (heights) and current (speeds) in tables and curves. Note that the
times of max for each are quite different at exactly the same point geographically.
Narrow necks in tidal areas can have vastly more powerful speeds than the same tidal range on more open areas of the same body of water. Which is essentially what Hell Gate is, a narrow neck, compared to LI Sound and even the width of the East River.
However, running down a single source river from high tide downstream is helpful because you're a cork floating on the highest water, which is gonna be lower later, so you "get the flushing action" and the current speed doesn't matter.
For instance, when I'm coming downriver from say Sacramento, here in California, I leave on the highest tide and run downriver, caring naught for the current speed 'cuz all I care about it that it's going the same direction than we are. It could get stronger in narrower reaches and slower in wider spots, but it's going in my direction.
However, when I get to San Francisco Bay, the currents, not following the tide, are what I really need, because the currents literally split in half right in the middle of the Bay, where the flood sets north and also south from that center line. I could care less about the height of the tide when I need to deal with the currents.
When I get to my anchorage is when I revert back to tide height as an issue.
I know the guys posting about going in and out on the west coast talk about doing it with the tide there also and I've looked at the tides on the GPS for locations there.
Given that, unless I'm on a river here, the ONLY information I need to know are the currents. Tidal height and time means nothing to me when I'm trying to go through the Golden Gate, ONLY the currents, their time and speed are important information.
We get mini-books that are about the size of two business cards put together for free from our chandleries that give hour-by-hour tables for both the tidal and current information, plus those charts showing direction and relative speeds. It's the most useful little book I have on board: the boat, the car and in the house.
It's also called "The Most Misunderstood Book in Town!"