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Old 07-10-2014, 15:25   #1
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Using an Outdated Eldridge Tide and Pilot Book

For academic exercise, does anyone know how to use an outdated version to derive new tide table for the present date. It may be need to use the lunar calendar to do the calculation.

Anyone know?
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Old 07-10-2014, 15:36   #2
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Re: Using an Outdated Eldridge Tide and Pilot Book

I take my old one and ................................. toss it in the trash.
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Old 07-10-2014, 18:50   #3
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Re: Using an Outdated Eldridge Tide and Pilot Book

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I take my old one and ................................. toss it in the trash.
LMAO. I think the academic exercise involves rockdawg trying to get something for nothing.
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Old 07-10-2014, 19:13   #4
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Re: Using an Outdated Eldridge Tide and Pilot Book

Depends how old.

"A well defined 1,800-year tidal cycle is associated with gradually shifting lunar declination from one episode of maximum tidal forcing on the centennial time-scale to the next. An amplitude modulation of this cycle occurs with an average period of about 5,000 years, associated with gradually shifting separation-intervals between perihelion and syzygy at maxima of the 1,800-year cycle."

So if your Eldridge goes back 1800 years, just add 1800 years to the dates to get an approximation. If you need it more accurately, you will need to take the 5000 year amplitude modulation into account.
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Old 07-10-2014, 19:47   #5
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Re: Using an Outdated Eldridge Tide and Pilot Book

I am not sure if I agree. The tide table should cycle thru every lunar month, not 1800 year cycle.

So if one given the high tide of 1:00 am at Hell Gate on Jan 1, 2014, one should be able to calculate when is the tide at Hall Gate on Oct 15, 2015. This should not be the rocket scientist stuff.
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Old 07-10-2014, 20:01   #6
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Re: Using an Outdated Eldridge Tide and Pilot Book

Just download the app tidedatafree.
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Old 07-10-2014, 20:10   #7
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Re: Using an Outdated Eldridge Tide and Pilot Book

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Just download the app tidedatafree.
But that is not as much fun as calculating with pencil and paper.
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Old 07-10-2014, 20:16   #8
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Re: Using an Outdated Eldridge Tide and Pilot Book

Take a look at the table of "Tidal Constituents" on this page:

Theory of tides - Wikipedia, the free encyclopedia

It's not a nice lunar monthly cycle. Note that there are about 30 harmonic components, only some of which are lunar month related, each with up to four different components, ranging from a period of hours up to approx 365.25 days. All interacting with each other.
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Old 07-10-2014, 21:06   #9
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Re: Using an Outdated Eldridge Tide and Pilot Book

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Originally Posted by rockDAWG View Post
But that is not as much fun as calculating with pencil and paper.
If Professor/Chief Science Officer rockDAWG visited the NOAA Science Center in Silver Spring, MD, and went to see 'Old Brass Brains' - the second of the analog computing machines used in the US to predict tides - he'd soon see why pencil and paper or even a room full of 算盘 cannot do the job.

To see 'Old Brass Brains', check out images #1621 - #1630 at the NOAA Photo Library.

Al
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Old 08-10-2014, 10:14   #10
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Re: Using an Outdated Eldridge Tide and Pilot Book

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Originally Posted by rockDAWG View Post
For academic exercise, does anyone know how to use an outdated version to derive new tide table for the present date. It may be need to use the lunar calendar to do the calculation.

Anyone know?
Use the Mayan calendar.
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Old 08-10-2014, 10:31   #11
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Re: Using an Outdated Eldridge Tide and Pilot Book

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Originally Posted by StuM View Post
Take a look at the table of "Tidal Constituents" on this page:

Theory of tides - Wikipedia, the free encyclopedia

It's not a nice lunar monthly cycle. Note that there are about 30 harmonic components, only some of which are lunar month related, each with up to four different components, ranging from a period of hours up to approx 365.25 days. All interacting with each other.
If one wants to predict the magnitude of the tide (how high or low?) it will reach at a particular day, I presume this will involve a complex mathematical model. However, if one simply wants to know when is the high or low tide, it should not be that complicated.

If one measure the high and low tides everyday for a year at a given location, I believe one should see the pattern how the tide repeats itself. I believe that is how the Almanac propagates their tide tables.
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Old 08-10-2014, 11:25   #12
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Re: Using an Outdated Eldridge Tide and Pilot Book

I use my old outdated Eldridge all the time. There hardly seems to be a reason to get a recent one. What I use it for is planning passages to hit a fair tide - especially when going through NYC/East River.

Their are lots of websites and chart plotters what will tell you what the tides are. Eldridge shows the currents at different offsets from the highs and lows - that's all I'm really interested in when planning. I suspect this relative data never changes much.
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Old 08-10-2014, 12:51   #13
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Re: Using an Outdated Eldridge Tide and Pilot Book

Tides? In NYC? Didn't anyone else get the memo, Bloomberg banned them before he left office, and the harbor has been dead flat ever since.

Otherwise there are so many free tide table apps for so many platforms...just use those and then you can still use the Eldridge charts for offsetting the currents, based on time of high tide.
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Old 08-10-2014, 14:55   #14
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Re: Using an Outdated Eldridge Tide and Pilot Book

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Tides? In NYC? Didn't anyone else get the memo, Bloomberg banned them before he left office, and the harbor has been dead flat ever since.

Otherwise there are so many free tide table apps for so many platforms...just use those and then you can still use the Eldridge charts for offsetting the currents, based on time of high tide.
He must have done something good in that case. Hell's Gate must be a piece of cake?
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Old 08-10-2014, 18:43   #15
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Re: Using an Outdated Eldridge Tide and Pilot Book

Hell's Gate actually IS a piece of cake. The Army undermined some 11 acres of the river bottom and dynamited it, about a hundred years ago, in what was then the world's largest explosion, in order to drop the river bottom over ten feet deeper and eliminate a couple of pesky rock islands in the process.

Hell's Gate today? Just feels like the water trolls are tugging at your rudder, or holding you in place. No big deal compared to trying not to get run down by commercial traffic that really has limited maneuvering options.
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