WatchUSeek Watch Forums banner

1 - 6 of 6 Posts

·
Registered
Joined
·
376 Posts
Discussion Starter #1 (Edited)
Once again I am going to visit a seaside location, so I would like to get this right this time round.

I have read on several occasions, over and over, that "tidal tables ignore DST".

I have also read that "one should ignore DST when setting tital graph in Casio watches".

That would mean one has to enter for the "high time" when setting the tidal graph in the watch exactly what it says in the tide tables, right?

But then I go to BBC Weather | Eastbourne
and right at the bottom I can read "all times are BST (Europe/London, GMT+0100)". So this one will be an exceptional table which does not ignore BST?

So far so good. Now the high tide is 1:08 -- as I understand it -- BST = summer time, which corresponds to 0:08 "winter time" (GMT).

And because it says "The high tide setting is not affected by the DST setting of the Timekeeping Mode." in the manual, so if I turned the DST off, the watch would show 0:08 at the time when the high time was --- I enter 0:08 as the high tide time.

Link to the manual I used: http://ftp.casio.co.jp/pub/world_manual/wat/en/qw3134.pdf

Then I read in the table 7:53 is low tide (this would be BST as the table is supposed to be in BST).

But in spite of all this, when it was as early as 7:40 (BST, as shown in the timekeeping mode of my watch, as we do have the summer time in effect now), i.e. 13 min before the low tide, the tide graph showed "one step above/after" the low tide!

Something is not right here. One of these things (or my understanding of it) must be wrong and I would like to know what it is :-s

Thanks for any ideas or explanations...
 

·
Registered
Joined
·
29,512 Posts
I understand the question but can't provide the answer...

Eastbourne should be very pleasant though, with this turn in the weather.
 

·
Registered
Joined
·
376 Posts
Discussion Starter #3
Well... the weather was fantastic :)

And I think I know the answer to my question now...

1. The tide tables at bbc.co.uk do ignore DST and are actually in GMT

At the bottom of the page (link in my first post) it says "all times in BST (UTC+1)" but this is simply not true. This may relate to the times of radio and TV programmes, or times for the weather forecast, like where it says "sunny" or "cloudy" or whatever. Due to regretably misleading design of the webpage one may suppose that it also relates to the tidal tables, which it does not. The times in tidal tables are in GMT (UTC+0). Only it does not say so anywhere.

What makes me think so? Well, on other websites e.g. this one I found tide tables with times approximately 1 hour "greater" than the times on BBC website. The only solution to this (other than one of the website is simply wrong) is that the BBC website gives times in UTC+0 and the other websites give times in UTC+1 i.e. British Summer Time for the convenience of the citizens, who use BST in their daily lives.

Also, for Sunday 2011-04-10 the BBC website gave a high tide time 14:52. I went to the seaside at approx 15:00 BST and then one hour later i.e. 16:00 BST (== 15:00 GMT). I observed that the tide was higher at 16:00 BST.

But this is not the end of the story! There is one more reason why my "tide graph" did not work as expected!

2. The Hight Tide Time setting for the Tide Graph does not ignore the DST setting of the timekeeping mode, i.e. the high tide time it must be set in accordance to the time zone used in the timekeeping mode taking also the DST offset into account

A simple experiment can prove this. Now it is 22:20 DST. If we were to ignore the DST setting, we would say it is 21:20. It actually is 21:20 ("standard" i.e. "winter" time), only my watch says 22:20 and everybody in the country will tell you it is 22:20, only because DST is in effect.

Now I set the high tide time to 21:00 (which should be only 20 min before now, if we were to ignore the DST). Now I switch to timekeeping mode and look at the tide graph: it shows one step below/after high time. If I set the high tide time to 22:00, it shows highest tide on the graph naturally. With high tide time set to 22:40 it shows still the highest tide.

Okay, now the time to cheat my watch :D I enter the setting mode and set DST to off!! Now the watch is showing "winter time". And, guess what, the tide graph is behaving differently: with the high tide time set to 21:00 it shows the highest tide on the graph, then with the high tide time set to 22:00 it shows highest tide still, but with the high tide time set to 22:40 it shows "one step below/before the high tide".

Clearly, with the same times set as high tide times, the tide graph behaves differently depending on the DST setting of the timekeeping mode.

Therefore Casio is wrong in saying that "The high tide setting is not affected by the DST setting of the Timekeeping Mode." -- or the sentence means something totally different from what I believed it to mean.

So it turns out that everything they were saying to me was wrong? And I believed BBC and Casio were always right? Whom can I trust now? Am I not too paranoid? Do you have similar experiences with Casio tide graph and DST? Or is the flaw only specific to this module (3134)? Too many question marks?
 

·
Registered
Joined
·
376 Posts
Discussion Starter #4
I was going to write to BBC, but I was procrastinating for a while, so... apparently somebody else did or they picked up on the thing themselves.

When I go to the BBC website now, it now says "all times BST unless otherwise stated" and in the tidal tables next to all time indications it says "UTC".

BBC well done for making your website clear and correct :)

But I should probably write to Casio asking them how it is with the tide graph on their watches...
 

·
Registered
Joined
·
12 Posts
Can I ask a favor from anyone with a G-shock tidal watch...

Can you please try setting your watch as if you live in Victoria BC Canada. Here is the website with the proper tidal info based on July 10 2011 Date. So if you start by changing back the date and then set the proper calculations using the info below:

a. World time is set to Vancouver
b. Daylight saving should be on (i think)
c. Moon Rise and Set in Victoria BC Canada = Moonrise, Moonset and Moonphase for Canada – British Columbia – Victoria – juni 2011
d. High Tide low Tide = Tides at Victoria, British Columbia

These are the settings that I think they should be, however I might be wrong, so if you could please double check using the above information.
my utc is -8.
longitude is 123 W
INT IS 2:06

Then once you think you have the correct settings advance the date into the future and see if the high tide and low tide match up using the above sites.
I would really appreciate the help if anyone is out there who is willing to do so.

Thank you so much! I love my Gshock. I'm just really frustrated that I can't figure out the Tide calculations.

Thanks Wayne.
You can email me direct at [email protected]
 
1 - 6 of 6 Posts
Top