# Tide clock
**URL:** https://boards.straightdope.com/t/tide-clock/815198
**Category:** Factual Questions
**Created:** [May 31, 2018, 3:14pm UTC](https://boards.straightdope.com/t/tide-clock/815198 "2018-05-31T15:14:51Z")
**Posts on this page:** 13
**Page:** 1
### Author:  [@MikeF](https://boards.straightdope.com/u/MikeF)
#### Post date: [May 31, 2018, 3:14pm UTC](https://boards.straightdope.com/t/tide-clock/815198/1 "2018-05-31T15:14:51Z")
Is there such a thing as a digital tide clock that will tell you when the next high/low tides will occur? My understanding is that on the mid-Atlantic Coast tides are pretty consistent so the X hours Until High/Low Tide are pretty accurate but having the actual time of the next two tides at a glance would be nice.
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### Author:  [@Procrustus](https://boards.straightdope.com/u/Procrustus)
#### Post date: [May 31, 2018, 3:20pm UTC](https://boards.straightdope.com/t/tide-clock/815198/2 "2018-05-31T15:20:06Z")
I would love that. There are apps that show the tides, which we use, but a clock would be a great idea.
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### Author:  [@Hampshire](https://boards.straightdope.com/u/Hampshire)
#### Post date: [May 31, 2018, 3:26pm UTC](https://boards.straightdope.com/t/tide-clock/815198/3 "2018-05-31T15:26:51Z")
are you looking for something different than a basic [tide watch](https://www.ripcurl.com/us/shop/watches/?page=1)?
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### Author:  [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)
#### Post date: [May 31, 2018, 3:33pm UTC](https://boards.straightdope.com/t/tide-clock/815198/4 "2018-05-31T15:33:07Z")
I’ve seen analog Tide Clocks, but until this thread, never a digital one
> **[Tide Clocks](https://tideclocks.com/collections/tide-clocks)**
My understanding is that tide clocks are manufactured for particular locations, because geography, as well as the positions of the moon and sun, also profoundly affect the tides, and ther are certain areas where the calculations are too complex for a simple analog tide clock. You’d think that programming such things for digital tide clock would be much more tractable a problem.
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### Author:  [@Philster](https://boards.straightdope.com/u/Philster)
#### Post date: [May 31, 2018, 3:52pm UTC](https://boards.straightdope.com/t/tide-clock/815198/5 "2018-05-31T15:52:29Z")
Yep, here’s an example of an East Coast time tide clock, with LCD countdown contrasting against the digital time. $$$
> **[Maximum-CSB Cronus Digital East Coast Time & Tide Clock ...](https://www.pleasureboatmarine.com/dieacotiticl.html)**
>
> Cronus Digital East Coast Time & Tide Clock - Brass Case, Black Dial \Time and east coast tide clock housed in a solid brass case with black dial and red numerals.\\Cronus time and tide clock offers a digital display ...
Not exactly as you wish, but I think the LCD countdown is digital in nature, but analog-ish in display (and analog is better and more accurate. Digital is a simpler display, but analog is best. The sun, the moon and the tides are analog in real life)
More in the spirit of OP’s request
> **[Amazon.com: Wend Digital Tide Clock North America - Pacific/Atlantic/Gulf of...](https://www.amazon.com/Wend-Digital-Clock-North-America/dp/B01HFBH0Y0)**
>
> Buy Wend Digital Tide Clock North America - Pacific/Atlantic/Gulf of Mexico : USA, Canada - 5,500+ Sites Across The Continent. Plus Digital Aquarium.: Patio, Lawn & Garden - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
.
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### Author:  [@Philster](https://boards.straightdope.com/u/Philster)
#### Post date: [May 31, 2018, 3:59pm UTC](https://boards.straightdope.com/t/tide-clock/815198/6 "2018-05-31T15:59:02Z")
Oh, btw… Tide times apps for smartphones are digital. Such as Tides Near Me.
.
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### Author:  [@MikeF](https://boards.straightdope.com/u/MikeF)
#### Post date: [May 31, 2018, 7:29pm UTC](https://boards.straightdope.com/t/tide-clock/815198/7 "2018-05-31T19:29:00Z")
So, based on Philster’s and Hampshire’s finds, the technology is there. The digital clock Philster points out is pretty much what I’m looking for although the display is less than ideal. Our boating is pretty tide-dependent due to shoaling near our marina. I already wear a watch that I don’t want to change and the phone app I have (Boats USA) requires Google Play Services to be turned on. That really drains my battery and only turn it on when I need it. I may order that one on Amazon. I wonder why there aren’t more of these things being made.
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### Author:  [@Mops](https://boards.straightdope.com/u/Mops)
#### Post date: [May 31, 2018, 8:40pm UTC](https://boards.straightdope.com/t/tide-clock/815198/8 "2018-05-31T20:40:10Z")
> [@MikeF](#):
>
> … I already wear a watch that I don’t want to change and the phone app I have (Boats USA) requires Google Play Services to be turned on. That really drains my battery and only turn it on when …
If there is a reason not to use a smartphone app, what about using an old school _printed_ tide table, like people did before apps?
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### Author:  [@Meurglys](https://boards.straightdope.com/u/Meurglys)
#### Post date: [June 2, 2018, 9:33am UTC](https://boards.straightdope.com/t/tide-clock/815198/9 "2018-06-02T09:33:10Z")
I used to haver an analog tidal clock, which was quite nifty.
Now I get a daily tweet with the local (Leith) tide times. I don’t always see it in my feed but I know it’ll be there and I can easily check for it. It is a working port though, with several marinas close by, and I expect many places won’t have a similar service.
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### Author:  [@DesertDog](https://boards.straightdope.com/u/DesertDog)
#### Post date: [June 3, 2018, 12:11pm UTC](https://boards.straightdope.com/t/tide-clock/815198/10 "2018-06-03T12:11:08Z")
> [@Mops](#):
>
> If there is a reason not to use a smartphone app, what about using an old school _printed_ tide table, like people did before apps?
\How 19th century.
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### Author:  [@MikeS](https://boards.straightdope.com/u/MikeS)
#### Post date: [June 3, 2018, 2:38pm UTC](https://boards.straightdope.com/t/tide-clock/815198/11 "2018-06-03T14:38:04Z")
> [@CalMeacham](#):
>
> My understanding is that tide clocks are manufactured for particular locations, because geography, as well as the positions of the moon and sun, also profoundly affect the tides, and ther are certain areas where the calculations are too complex for a simple analog tide clock. You’d think that programming such things for digital tide clock would be much more tractable a problem.
Your understanding is basically correct. This gives me an opening to talk about harmonic analysis of the tides, which I find fascinating.
The basic idea behind tide clocks is that the height of the tide can be expressed as the sum of a bunch of sine waves with various phase offsets:
h(t) = A[sub]1[/sub] sin(f[sub]1[/sub] t + δ[sub]1[/sub]) + A[sub]2[/sub] sin(f[sub]2[/sub] t + δ[sub]2[/sub]) + A[sub]3[/sub] sin(f[sub]3[/sub] t + δ[sub]3[/sub]) + …
Here, the f[sub]i[/sub]'s are the frequencies of each sine wave, the A[sub]i[/sub]'s are the amplitudes, and the δ[sub]i[/sub]'s are their phases. Each one of these terms is called a “tidal consituent”. The frequencies of the tidal constituents are pretty much the same everywhere in the world; they correspond to frequencies like the rotation frequency of the earth, the orbital frequency of the earth and the moon, and a couple other orbital properties of the moon (they have to do with its precession.) However, the phases and amplitudes depend quite heavily on local topography. This information is often tabulated; the NOAA has [a website where you can look them up](https://tidesandcurrents.noaa.gov/harcon.html?id=8459338&type=) for various locations, for example.
There are quite a few known tidal constituents out there; but many of them have small amplitudes and can often be neglected. The NOAA page above lists 37 constituents; but for Block Island (the location I linked to in the NOAA page above), only three have a greater peak-to-peak variation of more than six inches. However, in other locations, you might need more than three tidal constituents to make predictions to the same accuracy.
If you want to turn these numbers into a prediction, and you haven’t gotten around to inventing a digital computer yet, then calculating the height of the tide at any particular time is a pain, and calculating a useful table of tide heights for the next year (say) is extremely laborious. Devices called [tide-predicting machines](https://en.wikipedia.org/wiki/Tide-predicting_machine) were invented that allowed the user to create graphs of tide heights for long periods of time. These machines could be adjusted to allow for the variations in the A[sub]i[/sub] and δ[sub]i[/sub] coefficients in different geographic locations.
Of course, if you have a digital computer, and you know the amplitudes and phases of the tidal constituents at a given location, then creating these plots is a pretty simple exercise. But, again, you need to know these constants before you can make any predictions.
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### Author:  [@MikeS](https://boards.straightdope.com/u/MikeS)
#### Post date: [June 3, 2018, 2:46pm UTC](https://boards.straightdope.com/t/tide-clock/815198/12 "2018-06-03T14:46:03Z")
Oh, I meant to mention: If you want to learn more about the mathematics and the history of this topic, the American Mathematical Society did a nice series of popular-level articles on the subject a few years back. [Part I](http://www.ams.org/publicoutreach/feature-column/fcarc-tidesi1), [Part II](http://www.ams.org/publicoutreach/feature-column/fcarc-tidesii1), [Part III](http://www.ams.org/publicoutreach/feature-column/fcarc-tidesiii1).
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### Author:  [@Ornery\_Bob](https://boards.straightdope.com/u/Ornery_Bob)
#### Post date: [June 4, 2018, 1:44am UTC](https://boards.straightdope.com/t/tide-clock/815198/13 "2018-06-04T01:44:39Z")
I haven’t found any tidal apps I like, so before I hit the water, I use my desktop to go to my favorite tidal info site ([tides4fishing.com](http://tides4fishing.com)) and then I take a picture of the monitor with my phone. All the day’s info in a format I prefer over the apps I’ve found. I don’t just want times, I also want to see the tidal coefficient in graphic format.