Roy Lightning asked:
I often do a lot of walking and so I like to know when the tide is right out because I like to walk out as far as I possibly can. When I was looking at the tide times I thought, "how do they get it so accurate?" It will say something like Wells Bar, low tide 14:02. The question was really how do they get it accurate like that and who needs it that accurate because I certainly don't?
Dr Ken George, University of Plymouth, Institute of Marine Studies.
There are probably hundreds of examples of why people need to know times of high and low tide, like getting ships that have run aground, afloat again.
I would have though is less important to know the exact time of low and high tide, as to know the time when the tide will reach above, or below, a certain point; and this will determine whether you can float at a given level, or whether a certain section of beach will be exposed. Thus, that point might be reached at a different time relative to high tide for a spring tide as for a neap tide.
Once you know the exact time of high and low tide, you can then use various tables to calculate tide hight at any given time. If you ever do any sailing qualifications, there are loads of questions asking you things like what is the earlist time you can get under a certain bridge if you vessel is such and such a hight.
We in the British Isles and coastal Europe are so familiar with our large tides that we tend to forget how weird the tides in this area really are. In fact the North Sea has two tidal "gyres" or spots out at sea where it is high tide all the time and the tides effectively circulate around that point. The comments about the Southampton double tide fail to point out one of the reasons why the tides are in opposition between Dover and Lands end is that the tide coming down the North Sea is delayed differently from that coming up the channel.
There are quite a lot of places around the west coast of Scotland that are very tidal, the Gulf of Corryvreckan for instance, which has the third largest whirlpool in the world.
I notice, no factor of the seabed in the calculation of tides surely the angle or shape of the rise to the shore has some contributing factor, why for instance are there variations in depth of tides at different locations?
The only way to calculate tides properly is to do lots of measurements at the location where the tide is to be calculated. Even then, as has been mentioned, it will be affected by the weather conditions. I believe most tide tables, at least for British ports, are done exactly this way. Tidal calculations based on harmonic models are much less accurate.
who cares the world is my trashcan... ?, Thu, 27th Nov 2008
I am working on a project that deals with marine (vessel) casualties, specifically barge groundings. I was wondering if any of you would know if it's possible to pinpoint an area that is a "hot spot" for groundings. I gathered information for 13 months and two places are indicative of most groundings: Bolivar Penninsula Area & Brazos Flood Gates (Both are in near Galveston, TX). I spoke with a scientist from NOAA and he said that MLLW is what it's used to create nautical charts. My question is how can I use this data to prove that groundingsa are in fact happening in this two areas vice the rest of the Gulf Intracoastal Waterway? Boricua de Ponce, Thu, 4th Dec 2008