Tidal Differences

[alahol2]

I wonder if anyone knows of a table of tidal differences for the UK all based on a single port eg Dover (probably). Or even a table of differences between standard ports. That way all tidal calculations for anywhere in the UK could be done with a single set of tide tables (+ the table of differences).
Is there any reason why this wouldn't work? I understand that differences could be 12 or more hours but surely there must be some correlation between the tide at (say) Dover and the tide at (say) Ullapool?

I first wondered this donkeys years ago when I couldn't afford a new almanac every year (still can't) and wanted to sail outside my normal area for which I had current tables. I spent ages trying to correlate the tides at 2 different standard ports from the aged almanac.

 

[Twister_Ken]

I wonder if anyone knows of a table of tidal differences for the UK all based on a single port eg Dover (probably). Or even a table of differences between standard ports. That way all tidal calculations for anywhere in the UK could be done with a single set of tide tables (+ the table of differences).
Is there any reason why this wouldn't work? I understand that differences could be 12 or more hours but surely there must be some correlation between the tide at (say) Dover and the tide at (say) Ullapool?

I first wondered this donkeys years ago when I couldn't afford a new almanac every year (still can't) and wanted to sail outside my normal area for which I had current tables. I spent ages trying to correlate the tides at 2 different standard ports from the aged almanac.

Why bother? It's all available online, with no maths.

 

[MoodySabre]

Quite a few here based on Liverpool

 

[VicS]

I wonder if anyone knows of a table of tidal differences for the UK all based on a single port eg Dover (probably)

Yep marked on the maps in older AA handbooks.
Not sure exactly when they stopped doing it but they are in the 1988/89 one.
Based on London Bridge

 

[DJE]

In the French Bloc Marine almanac there is a chart with contours joining lines of equal time of high water. I believe the equivalent UK data is on Admiralty Co-Tidal Chart 5058.

The picture in the Bloc Marine shows this sort of thing:-

From here: http://thames.me.uk/s00030.htm

Presumably the Admiralty chart has more detail but there are both time and tidal range lines shown so you should be able to work out heights but not with a great deal of accuracy.

 

[Flashy]

Is there any reason why this wouldn't work?

I'm not sure how simplistic secondary ports data would be able to describe the difference between somewhere with simple tidal variation and somewhere with a double high i.e. Southampton.

 

[alahol2]

Why bother? It's all available online, with no maths.

When I first tried to do it the interweb hadn't been invented and now I haven't got a computer on the boat (nor a capable phone either).
Just thought it would be a useful table to keep on board that never goes out of date and may, one day, just come in handy. Same as all the old bits of rope and string in the locker.

 

[alahol2]

Quite a few here based on Liverpool

That's a very good start, it includes Portsmouth for which I've always got tables so all the others are calculable. I may just while away the hours and try to set up a spreadsheet to expand it a bit.

AA handbooks? I'll have to start looking on Ebay...

May just get hold of one of those Admiralty charts.

What about height differences(Springs & Neaps), or is that just too much to hope for?

 

[VicS]

AA handbooks? I'll have to start looking on Ebay...

Now there's a thought. Do you reckon I could sell some of my old ones?

 

[alahol2]

Now there's a thought. Do you reckon I could sell some of my old ones?

Just had a look, plenty on there going for between 99p and £20 (+ postage).
You could be onto a good thing.

 

[doug748]

I wonder if anyone knows of a table of tidal differences for the UK all based on a single port eg Dover (probably)...

I asked this ages ago with no luck.

However, Reeds gives you the info you need for all ports as far as Spain.

I only buy a new Dover tide table each year. If you also get an old copy of Reeve-Fowkes for the channel (the new ones are based on Cherbourg) you are in clover.

If you do decide to tabulate all the differences and make a booklet I would buy one for a start.

 

[LadyInBed]

Go to http://www.doverport.co.uk/?page=Marina
At the bottom of the page you will see Dover Marina Guide 2012.pdf
down load it and near the end after the Dover tides, there is a list of differences on Dover

This is a list that I have compiled:

Tide difference on	
H W Dover	
St Mary's	+6:07
Penzance	+6:05
Falmouth	-5:58
Fowey	-5:40
Plymouth	-5:28
Salcombe	-5:23
Dartmouth	-5:00
Torquay	-4:53
Exmouth	-4:48
Portland	-4:23
Christchurch	-2:01
Lymington	-0:41
Yarmouth	-0:36
Southampton	-0:01
Cowes	+0:29
Hamble	+0:30
Portsmouth	+0:29
Chichester	+0:27
Littlehampton	+0:19
Shoreham	+0:10
Brighton	+0:03
Newhaven	+0:05
Rye	-0:02
Folkestone	-0:12

Braye	-4:00
St Peter Port	-4:39
St Helier	-4:45

Raz de Sein	+5:13
Douarnenez	+5:11
Brest	+5:23
Roscoff	-6:02
Morlaix	-5:57
Treguier	-5:41
Lezardrieux	-5:13
Pampol	-5:15
St Malo	-5:06
Granville	-5:01
Cherbourg	-3:05
St Vaast	-2:05
Ouistreham	-1:28
Le Havre	-1:00
Fecamp	-0:29
Dieppe	-0:09
Boulogne	+0:11
Calais	+0:42
Dunkirk	+1:00
Ostend	+1:22
Zeebrugge	+1:40

 

[Mudisox]

For years the old mariners did without tide tables.
However they knew that springs occurred 2 days after the moon, and High tide Dover was around noon then.
Within all the variations of pressure, wind direction and other bits and bobs it seemed to work quite well. Made them think rather than looking it up and thinking it was for real.

 

[dt4134]

If you do try to base your calculations on the differences from Dover do so with a large pinch of salt. I've found differences that were more than 60 minutes more than the differences between the local primary port and Dover that Reeds had used for their tidal charts.

I believe Reeve-Fowkes also found significant inaccuracies and variations which is why he switched to using Cherbourg in later versions of his tidal atlases.

 

[fergie_mac66]

Yep marked on the maps in older AA handbooks.
Not sure exactly when they stopped doing it but they are in the 1988/89 one.
Based on London Bridge

Did the RAC do the same

 

[peterb]

In the French Bloc Marine almanac there is a chart with contours joining lines of equal time of high water. I believe the equivalent UK data is on Admiralty Co-Tidal Chart 5058.

The picture in the Bloc Marine shows this sort of thing:-

From here: http://thames.me.uk/s00030.htm

Presumably the Admiralty chart has more detail but there are both time and tidal range lines shown so you should be able to work out heights but not with a great deal of accuracy.

Yes, 5058 shows more or less the same lines, except that there are twice as many. The lines shown in Bloc Marine cover time in hours and ranges in metres, whilst 5058 works to half-hours and half-metres. The lines give the tidal times with respect to the time at which the moon is due south of Greenwich.

The red lines on the chart give time differences, the blue lines give mean spring range. You'll notice that there are some points on the chart where the red lines converge, while the blue lines make circles. These points (technically called amphidromic points) apparently have higth water all the time; but that's because they have virtually zero rise and fall. Don't trust the curves near those points because higher harmonics come into play. To see the effects look at the time corrections for Port Ellen (Islay).

 

[doug748]

If you do try to base your calculations on the differences from Dover do so with a large pinch of salt. I've found differences that were more than 60 minutes more than the....

I have never unearthed a discrepancy as large as that.

 

[peterb]

I have never unearthed a discrepancy as large as that.

Try Port Ellen

 

[doug748]

Try Port Ellen

Not a descrepancy, just a difficult case.

 

[dt4134]

I have never unearthed a discrepancy as large as that.

Irish Sea. I was surprised to see such a discrepency too. Went with the tides based on the local primary port and it worked.