UKC

Tides, possibly one for those that sail too

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 David Coley 12 Oct 2021

Hi,

within the accuracy needed by climbers, and possibly leaving out some strange places like the double tides of Swanage, is the time of low tide at any place a constant offset from that at Dover - roughly?

Thanks.

 scott titt 12 Oct 2021
In reply to David Coley:

Yes, as long as you remember BST /UTC!

 deepsoup 12 Oct 2021
In reply to David Coley:

Yes, roughly.

Also the tide times in any given place will be at roughly the same time of day on any day at the same phase of the moon.  So if, for example, you know the time of high tide three days after the full moon this month it'll be within 25 mins or so three days after every full (and new) moon.

And (following on from that) spring and neap tides in any given location always happen at more or less the same time of day.

Edit to add:
The above is true if you remember what Scott said:

> Yes, as long as you remember BST /UTC!

Post edited at 13:55
 David Coley 12 Oct 2021
In reply to scott titt:

Thanks Jim.

I note that tide information several months out seems harder to get than it once was. The CC don't seem to do it, and the couple of apps I tried only did a few months ahead.

Back in the day, the news papers gave the tides times for Dover, and I always wondered that if the temporal offset was constant, why climbing guide books didn't just say, Chair Ladder = Dover + 6 hrs (or whatever it is) so had assumed the offset was not constant.

So, being Dover is available to 2023 or more would a list of offsets be useful, or is there a better App or website I need to go hunting for? 

Thanks again.

In reply to David Coley:

If you can find one the older AA atlas/handbooks used to have offset times (I think based on Tower Bridge?) marked on the map at various locations all round the UK coastline.

The following gives HW differences from Dover at a few locations:    https://montymariner.co.uk/articlessecondary-ports-correctiongrab-bagditch-kitsolent-drying-piles/cross-channel-brittany-distance-high-water-difference-to-dover/high-water-time-difference-to-high-water-dover/   And   https://www.tidetimes.org.uk/time-difference

Post edited at 14:14
In reply to David Coley:

> So, being Dover is available to 2023 or more would a list of offsets be useful, or is there a better App or website I need to go hunting for? 

What you need is a nautical almanac with a list of ports, or the relevant admiralty chart for the area. This will give you the offsets w.r.t. Dover. Charts will refer to 'standard ports' so you may need to extrapolate a bit. Alternatively, port authority or marina websites might give you links to local tide tables or the offset.

http://tides.digimap.gg gives tides out to the end of December 2024 for Guernsey.

In reply to David Coley:

The Easytide website has tide times for most places round the UK and gives a nice graph, which is especially useful for the areas from approx Southampton to Portland with super weird tides

https://easytide.admiralty.co.uk/

You can search or just zoom into the map

In reply to David Coley:

> I note that tide information several months out seems harder to get than it once was. The CC don't seem to do it, and the couple of apps I tried only did a few months ahead.

https://tides4fishing.com is the only one I've found that goes beyond a week.

Depends where you're going. You might be lucky, e.g. https://www.visitpembrokeshire.com/wp-content/uploads/Pembrokeshire-tide-times-table-2021.pdf

 ScraggyGoat 13 Oct 2021
In reply to David Coley:

Imray Tides Planner App.  

In app purchase of UK tides for around £3.50 gets you the whole of a years tide data for the Uk.  You can select virtually any port and put multiple ports from the UK into your favourites and then look up the high and low tide times, and height above datum at any time in the cycle, for any day in the year you have purchased.

also gives sunrise and sunset times and ditto for the moon as well.

In reply to stevevans5:

> The Easytide website has tide times for most places round the UK and gives a nice graph, which is especially useful for the areas from approx Southampton to Portland with super weird tides> https://easytide.admiralty.co.uk/

Thanks. I've previously used Magicseaweed which has similar graphs though the vertical axis for water level is more compressed. Magicseaweed also has information on weather, daylight hours and quite usefully information on swell.

 David Coley 13 Oct 2021
In reply to David Coley:

Thanks everyone. Does anyone know why the climbers club stopped issuing tide info?

I'm thinking about trips that might be planned a long way in advance. For example Lundy accommodation has just come on line for 2023.

If someone understood computers, we could put something together for use by the community using xtide?

 ScraggyGoat 13 Oct 2021
In reply to David Coley:

Tidal data is put together (from memory) by the UK Hydrographic office (UKHO), they allow free access upto seven days in advance from the current date.

Publishing their tidal predictions beyond that is a copyright offence unless a licensed reseller, which might have been why the CC stopped.  A number of websites and other organisation faced a clamp down.

You can get ‘quick tide’ calculators, but the further ahead the larger the error, as it’s not a simple task/shift.  Tide predictions vary depending on extrapolation method used, tidal data available, and the constant from Dover isn’t static varying a bit from springs to neaps in many places, plus the natural change in tide.  Accurate prediction thus requires complex algorithms, which unsurprising the UKHO & The Admiralty have.

But what I’m trying to say is if you are looking a couple of years ahead without paying, using a free source, adjusting by a constant, the time of HW could be out by maybe an hour, possibly more.

A quick search without pointing you to expensive  tomes gave this simple list of Tidal constants from Dover for a variety of ports as a starting point:

https://www.wansbeckpaddlesports.co.uk/tidal-constants

 I have no knowledge of how accurate it is, as mentioned above getting an old sailing almanac would also give constants.

Its easier just to buy the tides. £3.50 for the whole of the UK for a year is stunningly cheap, not that long ago tide tables for a just couple of ports would cost that.

As for UKHO 2023, I’m not sure when they will be issued at a price for the likes of you and I, but shouldn’t be too long as we are getting to year end.

Post edited at 00:07
 deepsoup 14 Oct 2021
In reply to ScraggyGoat:

> You can get ‘quick tide’ calculators, but the further ahead the larger the error, as it’s not a simple task/shift.

You make it sound like a weather forecast, but it's more of an astronomical thing - it's an academic nitpick, but over years and decades the error would be more of a cyclical thing wouldn't it?  Further ahead might be a smaller error than less far ahead if it means conditions more closely aligned to whatever you're extrapolating from.  Springs/neaps, full/new Moon, equinox or winter/summer solstice etc. - ultimately I guess over the 19 year period it takes for the Moon to come back to the same position relative to Earth and Sun that it's in today.

> But what I’m trying to say is if you are looking a couple of years ahead without paying, using a free source, adjusting by a constant, the time of HW could be out by maybe an hour, possibly more.

An hour seems a little bit pessimistic to me, but even so that's near enough to plan a climbing holiday isn't it?  I'd have thought if you have ambitions to do tidal sea cliff routes you're basically just wanting low water to be noon ish or early afternoon - late enough that the rock's not going to feel greasy, early enough that there's still plenty of daylight left.

Having a quick look at some tide tables for Lundy that seems to mean a few days before springs there, so around new or full Moon.  There's no problem finding 2023 dates for those for free.

> Its easier just to buy the tides. £3.50 for the whole of the UK for a year is stunningly cheap, not that long ago tide tables for a just couple of ports would cost that.

I have the David Easton 'Tides' app on my (Android) phone.  £1.89 to buy, no adverts, no in-app purchases.  It uses a variety of sources including UKHO for the UK (presumably only within the 7 days that the data is free).  Short range predictions include 'storm surge' and swell forecasts along with the astronomical tide, and it seems to be happy to extrapolate indefinitely far into the future (or past).

 Mark Bull 15 Oct 2021
In reply to David Coley:

If you don't want to rely on modern technology, this cardboard device works on the fixed offset principle: http://www.quicktide.co.uk/ (just gives times, not heights, though). 

In reply to deepsoup:

> Having a quick look at some tide tables for Lundy that seems to mean a few days before springs there, so around new or full Moon.  There's no problem finding 2023 dates for those for free.

^^ this. Once you know when spring/neap LW times are for your chosen location just look at moon phases. Springs are always New / full Moon and 2-3 days after. New moon low waters are always slightly lower than full moon low waters, and full moon HW is always higher than new moon HW (10-20cm here on a 10m range for both).


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