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Tide times without tide tables?


Crid
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OK, a slightly odd question here. I'm not completely sure it even belongs in this forum, but here goes...

 

My GPS units don't have marine maps on them, so I don't have Tide Prediction Stations. However, both of them can give me moon rise/set times for wherever I happen to be. So is it possible to work out when low/high tide is from this information, even if you can't work out HOW low or high the tide will be?

 

It is a caching question of sorts. On vacation last year I went after a cache on a tiny island that could be walked to at low tide. I failed to find it and I will be going to the same place on vacation next year. Not only that, I've just been checking caches in that area and a second one has now popped up on a different tiny island that can only be reached at low tide.

 

I'm guessing high tide is at the moon's equivalent of midnight and noon (moon directly overhead, or on the opposite side of the earth) and low tide is halfway between high tides? Moon Noon (for want of a better name) is presumably halfway between moon rise and moon set? Or is it more complicated than that?

Edited by Crid
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If you own a Garmin Mapsource product, even if without a tides feature, you can download a tide information product. I did this last year, so as long as things haven't changed, it might work for you too. I have even uploaded this mapset to a Legend CX and an iQue M5 and can get the points to calculate the tides on the unit! Somewhat interesting for my recent trip to Hawaii, although the tides are not much of a factor there.

 

see:

http://www8.garmin.com/support/download_de...ct=010-00191-00

or

http://www8.garmin.com/support/download_de...ct=010-00199-00

 

Look for the "Download Recommended MapSource US Tides Software" paragraph, a 5.13MB download.

 

Proceed carefully, I have not had any problems, but Garmin may have changed something...

 

Hope that helps...

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Thanks for the replies. Unfortunately I won't be able to get my laptop online where I'm going and I don't have a PDA. My hope was that I could work things out from the information the GPS calculates, but it seems I won't be able to do that. And as somebody pointed out, I'm in the UK so the Garmin download won't work for me.

 

Thanks for the information link Gallet, although I see they talk about centrifugal force...

 

centrifugal_force.png

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In the UK you can get tidal predictions for today and up to 6 days in advance for free from ...

 

http://easytide.ukho.gov.uk/EasyTide/EasyT...SelectPort.aspx

 

So just print out the tide tables for some of the places you want to visit in advance (assuming you're not away from a computer for more than 7 days before your visit to a particular place!).

 

On the other hand, if you're wanting to visit some of these small islands separated by causeways, you can't always rely on tide predictions alone, as you don't really know how much time either side if low tide you have to complete your crossing. In these cases it's best to Google the island in question and see what the recommended crossing times are, for example for Lindisfarne ...

 

http://www.northumberlandlife.org/holy-island/Page2.asp

 

Unfortunately in the UK the UKHO (UK Hydrological Office) have copyright on tide information and it's not public domain (and therefore free to the likes of Garmin) like it would be in the US.

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Thanks for the replies. Unfortunately I won't be able to get my laptop online where I'm going and I don't have a PDA. My hope was that I could work things out from the information the GPS calculates, but it seems I won't be able to do that. And as somebody pointed out, I'm in the UK so the Garmin download won't work for me.

 

Thanks for the information link Gallet, although I see they talk about centrifugal force...

If you will be taking a J2ME smartphone, you might be able to use µTide.

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OK, a slightly odd question here. I'm not completely sure it even belongs in this forum, but here goes...

 

My GPS units don't have marine maps on them, so I don't have Tide Prediction Stations. However, both of them can give me moon rise/set times for wherever I happen to be. So is it possible to work out when low/high tide is from this information, even if you can't work out HOW low or high the tide will be?

 

 

From reading... it seems you want to have 'in hand' tide calculations... I can't help with that, but you can get tide information (calculated) for almost anywhere in US/Can at http://www.almanac.com/astronomy/

 

I came across this looking for something else... I assume they publish a paper version perhaps...

You used to be able to get published tables at almost any marine outlet, or as a last resort, check the local docks in your hunt area... tides used to be posted on chalkboards for all sailors to see...

 

Doug VE7RXC

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1. Some GPS's have Moon Rise/Set times and Sun Rise/Set times.

2. Others have best fishing times related type times, totally arbitrary and mostly moon related?

3. Some have actual tide calculation capability (Delorme PN-20...)

 

My Magellan Gold has #1 above but the times seem to be completely at odds with reality when it comes to the Moon. Well not completely, sometimes up to a couple hours off. At first I though that it did calculate daylight savings time for the display and Sun times, but not for Moon times, but that doesn't seem to hold water.

 

Also, on the compass screen, the compass card screen and the highway screen, the popsition of the Sun is right on 100% of the time, while the Moon is sometimes up to 20 degrees away from where it really is.

 

I think Magellan uses a stupid algorithm that doesn't work for the Moon. I know they do some really dumb things in other parts of their firmware, WAAS anyone? And they do some really smart things too, go figure.

Edited by trainlove
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1. Some GPS's have Moon Rise/Set times and Sun Rise/Set times.

2. Others have best fishing times related type times, totally arbitrary and mostly moon related?

3. Some have actual tide calculation capability (Delorme PN-20...)

Most Garmin handhelds (except the newest ones) do all three. My Vista HCx will show a nice tide chart for a selected tide station on whichever day I choose.

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1. Some GPS's have Moon Rise/Set times and Sun Rise/Set times.

2. Others have best fishing times related type times, totally arbitrary and mostly moon related?

3. Some have actual tide calculation capability (Delorme PN-20...)

I believe the Hunt/ Fish predictions are based on so-called "SoLunar Theory" (Sol for Sun, Lunar for the Moon): http://www.solunar.com/the_solunar_theory.aspx

 

Personally, I think it is complete hokum - I can NEVER catch any fish, even when my GPSr shows it to be a great fishing day! :rolleyes:

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This applies to US, don't know about UK. When I was SCUBA diving (during a period in time when computers

used punch cards for data entry) there was available from dive shops, this marvelous little thing called (of all

things) a tide book. It cost like $00.75 USA, probably about $5.00 now, bet they're still around. I'm sure there's

salt water fishermen and open water divers in that locale, get one when you hit town.

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