The Lure Forums banner

Tidal Coefficients.

5483 Views 15 Replies 8 Participants Last post by  Ben Field
Just something to chew on.

been playing with this for some months now. I found this site and the tide coefficient data
completely by accident when researching other stuff.

I found the range data and mid tide height pointers quite useful.

I'm also getting keen on using coefficient in my fishing. apparently, in Europe, It is
quite common to do so already.

Take a look...
1 - 16 of 16 Posts
Looks good Keith. You're completely right, the French mags very rarely mention tidal height, only the coefficient. We do keep an eye on this for low water fishing - I'll explain next time I see you in case it helps.

A couple of things sprung to mind. The times are UTC+1 which is important if anyone is going to keep this site for future reference.

Also seeing St Helier mentioned reminds me that not everyone realises that LW and HW around the Island might be at slightly different times to St Helier.

I know a matter of 15 minutes might not sound important but in areas where bass are resting up over low water (when we can get the strongest tidal flows in some spots) missing half of the 30 minute window after the tide turns when they go back onto the feed could mean missing half of the prime time.

Not sure how this works/if this applies in the UK though.


See less See more
cheers Paul.

Yea, me an kev work off variable low/high data too.
St Helier times are NOT accurate enough for long range wading even 4 miles away
and it is misleading when Bass run too at various locations.

Good tip about the Tide times on that site.

And yes, explain it to me when I see you. Looks very useful.
OK, I am dumb, what the hell is all this? It looks to me like they are talking about the time from low til high, and when the tide is strongest? No? I still cant seem to work it out though, Paul will you show me too please.
Am I right in thinking you are talking about tide height at HW+ 3hours etc?
I found this on the Wiley Nautical site that may help...


We Brits (well some of us) use Range, the difference in metres between the heights of successive HWs and LWs, to measure the size of a tide. This in turn allows us to call a tide a big one or a small one, or to say that it is a Spring or Neap tide respectively – important information.

In order to arrive at this simple situation you have to look up the heights of HW and LW at the Port and on the day in question and this takes a little time. Such figures will be different whether you are in Oban or off Shoreham, so do not readily stick in the brain cell. There is a better way, much better, for which we have to thank the French (along with good wine, food and cheese). That is Coefficients ...

A Coefficient, whatever the application, is simply a non-dimensional way of expressing size. Non-dimensional means that it doesn’t matter whether we are measuring in feet, metres, lbs avoirdupois or in peanuts or bananas. So the people at SHOM, the French Hydrographic office in Brest, produce a table of tidal coefficients for the year, every day, morning and afternoon.

You, the hard-pressed Vasco, have to remember only 3 figures: 95, 70 and 45. Tack on 120 and 20 to cover the extremes and we can produce a small but meaningful table, comme ça:

120 = a very big Spring tide
95 = a Spring tide (vive eau)
70 = an average tide
45 = a Neap tide (morte eau)
20 = a very small Neap tide

These coefficients are valid whether you are in Leith, Dunkerque or Tilbury. If you doubt that, then think BIG: think Earth, Moon and Sun and little old Europe. Astronomical distances are so great that it is easy to accept that the whole of Europe is subject to the same lunar and solar influences at any one time.

In practical terms, just look up and record in your logbook the day’s coefficient, eg 43/42, just below Neaps – and plan accordingly. In France the times of access to a tidally limited port are often expressed in Coefficients, eg at Binic:
Coefficient 40-50, Access HW –1 to HW; 50-60, HW –1½ to +1¼ ... and so on.

In the Wiley Almanac we colour Spring dates in red, conventionally big and positive; and Neaps in blue, small and negative. Once you’ve got used to Coefficients (allow 5 minutes), you’ll never look back.

Hope this helps... :D
See less See more
As I've said, I have researched this somewhat but, still haven't grasped the whole concept.

What I do like is the fact that it removes metric/imperial data from the equation.

Believe me, I would classify myself as fairly clued up re local tidal flows etc..

Yet, If I forget the tide time exactly, I will use my mobile phone to check.
The data is meters. You know, I do not mind admitting, meters mean nothing to me
reference tides. I just cannot visualise meters in fishing. I even struggle with rod length.

And, I've done it for years and years. 11, 14, 16 meter pole fishing, no problem.
I'ver set my float at 7ft though, not in meters or cm. Who can honestly say....

I had a 1.25kg Bass or, my rod is 2.40 ? You'll use pounds and feet/inches

Why we have this issue is beyond me as I'm fairly good at absorbing new stuff.

The same with tide coefficients. It makes sense, sort of. I really want to absorb and utilise
this info in my fishing without making it more complex. Information is power and I feel
we might be missing something here.
See less See more
I kind of get it now, cheers Marc. I take it then its more handy for visiting yachtsmen etc? I mean I dont see the advantages?
I JUST DONT GET IT............ :rollineyes: :muttley:
One thing it tells you is how any tide compares relative to the preceding tide or the next tide. Sometimes the next tide is higher, but the relative increase is less than the tide before. If you see what I mean.
Do you know what confuses me? I am like Keith when he says he just dont get meters, I just cant get my head around them. And I also dont do low water sizes either, I tend to say its a 30ft low today. I know what I mean, thats a small nip. And I tend to be able to tell people what kind of height and time the tide is by being able to work it out from the last time I knew for sure, which can be a week earlier or more. So what I am saying is I am confused enough already but get away with it beautifly. I have no idea at this very moment what our tides or time are, but as a guess, total gues, I noticed it was a full moon a couple of nights ago, therefore I would say its a big tide and high about 9 oclock this evening, maybe later,mmm, stab in the dark, todays tide and time is a 34ft and it was high at 10 oclock this evening. I will go and look now. Oh by the way sorry for going off topic.

EDIT: OMG, just checked, its a 35.8ft tide and it was high this evening at 9.18, ah who need these french crazy tide explanations when you have spidey senses eh.
See less See more
Don't know why you are bothering to print tide books Mick. :badlol:
st ouen said:
One thing it tells you is how any tide compares relative to the preceding tide or the next tide. Sometimes the next tide is higher, but the relative increase is less than the tide before. If you see what I mean.
I translated that and it does help. Thanks.
So from the above info my understanding is this:

If you are "fluent" in local tides, understand the different rates of flood/ebb across the cycle and are happy with the effect on your marks, this coefficient data would just be another way of looking at that info (and might replace the need to view meters/feet etc).

But, if you travel elsewhere fishing, this would be a universal way of quickly looking at a weeks worth of coefficient tide data and being to accurately understand, whether the tides are big/small/unusual for the area you are in. Presumably, you can look at one set of coefficient data and apply it anywhere.

Does that sound right?

I have also noted that some big tides don't always come with lowest lows. Loads
of tidal variables that in detail, are hard to process quickly or on the fly.
Like has been mentioned atmospheric pressure makes a big difference, especially here
on our shallow, fast current SE.

Coefficient data sounds really simple and yet, it tells you quite alot.

I'd like to know what the tides where when Nathan and Rob had their best fishing of late too.

If there is one thing in fishing in the sea that influences fish the most, it must be tide and
associated current.

Sometimes, looking at the same data but in a new way can bring a clearer picture.
See less See more
One thing that I think it does add to our standard way of looking at it in 'heights' is that it makes it very, very easy to find the average tides at your location.

As well as the coefficient, it appears that the French always have the heights as well. To be honest, if I looked at a standard UK tide chart it would be difficult to work out what height the exact average spring or neap tide is, I could estimate but never be sure. Whereas with the coefficient you can immediately tell what the average is as it will coincide with a coefficient of 90 or 45. Why do you need to know the 'average' spring or neap tide height? Well.... you don't necessarily, but it's a useful marker by which to judge everything else. In our own tide charts, I don't belive we have a marker, or a standard set point by which to make comparisons?! Also, tides obviously vary in height around the UK. It may not be so useful on home soil but if you were to travel to another area, knowing the coefficient for that day (which will be the same all over Europe) you can judge in just the same way as you could at home whether the tide for that day was bigger or smaller than the average for that location - without knowing the area.

So, I think its basically most useful when it comes to comparing a tide in one location with that of another - without involving height!

i.e. the tides on the CI's are bigger than ours, but no matter of the distance between areas (over Europe) and how 'high' the tide is, we have a good comparison of when fish are feeding and being caught - without including the actual tide 'height' - which becomes irrelevant and is specific only to area.

In fact, I'm fairly sure I'll start using the tidal coefficient when building graphs and statistics of catches on my site.
See less See more
1 - 16 of 16 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.