Tidal Height Calcs

Re: dedicated rya quiz forum

Does it matter? Sometimes this forum can be a pretty bitchy place! Maybe it's better, if you don't see the point, just not to bother answering the question. I don't see the point in taking time in objecting to it.
 
Of course

following my own logic I shouldn't have bothered posting my response here!
 
Have been

responding to the hypothetical Scenario Poser thread, but so far no one has jumped down ghost's throat over that one. Why the one and not the other? Go for it! /forums/images/graemlins/wink.gif
 
Re: Have been

Read the questions again. Ghost is apparently asking for help with a question to which he doesn't know the answer. This one appears to know the answer and is testing us. It's all in the wording.
 
Re: Have been

[ QUOTE ]
Read the questions again. Ghost is apparently asking for help with a question to which he doesn't know the answer. This one appears to know the answer and is testing us. It's all in the wording.

[/ QUOTE ]

Read ghost's posts again. According to ghost he DOES know the answer, and he's trying to see if we know a trick that he has up his sleeve.

"What I'm looking for here is to see if anyone knows... a bit of seamanship, that would magically and mysteriously allow you to make that mark while matey looks on stupified "

Personally I don't mind too much whether the original poster knows the answer or not, the discussion can be interesting.

It is also useful as a reminder of the effect that barometric pressure has on tidal heights.
 
Re: Have been

Seems as if I have a touch of support so am encouraged to attempt to get to where I wanted the thread to lead to in the first place had we not become distracted.

The question of barometric pressure effecting tidal heights. It seems that a figure of 1015Mb was used in the thread as the average pressure that tidal heights are calculated on. In my YM exam when asked I got this question wrong and was informed it is 1013Mb. I soon realised if the average barometric pressure was used to calculate tidal height in different regions then the average pressure will surely be different. For example the Azores high. I have tried my best to find this information out but am at a loss. I think I read it is in Admiralty Pilots but on a month to month basis, the winter figures being naturally lower than the summer ones. Not the information required for these calculations. I am sure there are many people on this forum who will be fully aware of the source of this information and I look forward to reading the answer in due course.

MINESAPINT.
 
Re: Have been

Quote from Reeds: "average pressure is 1016 in southern England, 1011 in Scotland"

Only in the realms of RYA exams is there a 'right' answer. It's akin to working out tidal set to 1/100th of a mile while using a tidal diamond 10 miles away.

BTW, I didn't use the same method as you for calculating the tidal heights. Did you figure out how I did it? There are at least 3 common methods.
 
Re: Have been

I do have Reeds OKI 2005. I assume the average barometric pressures will be in but I still can't find them.

MINESAPINT.
 
Re: Have been

I have found a piece about barometric pressure in Reeds that I have highlighted previously page 180. "Mean sea level pressures are quoted in admiralty pilots: 1017 for example along the UK south coast in July 1014 in January 1013 at Wick in July 1007 in January".

MINESAPINT.
 
Re: Have been

No, the accompanying volume - "Reeds Nautical Companion"

The common methods are the tidal graph found in Reeds or ATT, the rule of twelfths and the method I used: tidal prediction software.
 
Re: Have been

Was getting irritated, but now see where you're coming from.

Real world pressures and tides. You go into wherever watching your depths on the way in. They're either greater or less than you expect. A glance at the baro might tell you why, or another look at the tide-table and have you allowed for summertime?

Good luck with the detailed calculations, let's hope you come to roughly the same results.
 
It is a waste of time in most places farting around to the accuracy expected in a Do it the RYA way exam anyhow.

The charted depths up north were probably last measured in 1894 and the sand is continually shifting. The chances of you being anywhere near are probably near 100 000 to 1.

Check the tide table, take off the figures from the standard port, read the pilot, arrive in the 2hrs either side of HW or so, follow the harbour channel and find the visitors moorings.

Do newly qualified skippers really sit up all night working out to 16th of an inch the tide height at the bar? Personally I would rather enjoy myself than go through this kind of pressure every time I sailed.
 
OK, by calc, ignoring barom. you need 3.6m. With stationary low, so pressure has time to alter height, you can assume that the surface will be raised in the order of 0.3m, so you need about 3.3m

Is that the answer you wanted?

Ignoring local effects like this is not the place to be?
 
[ QUOTE ]
What's the point of the questions.

Same question could be asked about the majority of posts.

Its quite simple. I recently took my Yachtmaster Offshore (power) which I passed by the skin of my teeth. I am planning to take the same exam under sail and am studying in order to consolidate my knowledge in the hope I will pass under sail more comfortably. There are a few subjects I know I am weak on and as well as books, internet and RYA courses I have been drawing from the considerable knowledge available on this forum. It is clear that my questions are not welcome so I will dissist from posting any more.

However if anyone is aware of a forum more suited to my needs I will be glad to hear of it. With I understand in the region of 22,000 people taking RYA courses every year I am surprised there is not already a dedicated forum.

MINESAPINT.

[/ QUOTE ]You asked in the right place. Don't worry if a few wasps get angry. Perhaps if you said why you asked the question, it would have been more peacefully and helpfully answered. Keep asking questions. I wish a few of the wasps would stay in the lounge where they belong /forums/images/graemlins/blush.gif
 
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