Tides

Simon0001 · 21 Nov 2021 at 22:18

I'm looking at tide charts and they say it's going to be 8m at high tide.

Where do they measure from? The sea bed? Surely that varies so how can I tell when the sea near me is having an exceptionally high tide

azazl187 · 21 Nov 2021 at 22:20

You would use a tide gauge

Graetzbridge · 21 Nov 2021 at 22:21

Simon0001 said:
I'm looking at tide charts and they say it's going to be 8m at high tide.

Where do they measure from? The sea bed? Surely that varies so how can I tell when the sea near me is having an exceptionally high tide

The surface - not the seabed.

Hagar · 21 Nov 2021 at 22:30

Simon0001 said:
I'm looking at tide charts and they say it's going to be 8m at high tide.

Where do they measure from? The sea bed? Surely that varies so how can I tell when the sea near me is having an exceptionally high tide

It is based on a tide datum, mean sea level at Newlyn Cornwall OD. All points and places around the coast are given a chart datum CD relative to Newlyn. CD is the lowest astronomical tide at that location and is below OD. I assume that 8m relates to LOCAL chart datum so that it would be less related to Newlyn

dlockers · 21 Nov 2021 at 22:41

Disappointed this thread isn't the usual lowbrow stuff.

englishpremier · 21 Nov 2021 at 22:43

Sounding are usually at mean lower low water (MLLW). This usually ensures that actual depths you encounter are higher than those charted but not always (given that it's a mean)

Add the tidal data to the MLLW to get the actual depths.

Some charts particularly in non-tidal areas might use mean sea level, but don't recall encountering it in my charts.

Basically these days though just something like tides4fishing or navionics and the work is done for you.

It can still be fun though working out when to cross various areas such as navigating the Messina Straight when all references are to HW in Gibraltar.

Dis86 · 21 Nov 2021 at 22:52

Simon0001 said:
I'm looking at tide charts and they say it's going to be 8m at high tide.

Where do they measure from? The sea bed? Surely that varies so how can I tell when the sea near me is having an exceptionally high tide

From chart datum. It will tell you on the chart.

[FnG]magnolia · 21 Nov 2021 at 22:59

8 metre high tide? Do you live in the popular film Point Break ?

Here are some tide facts for the beach 5 minutes from our house:

November 2021 Tide times, tide heights and tidal coefficients
Date 1st Tide 2nd Tide 3rd Tide 4th Tide Moon Sunrise Sunset Moonrise Moonset
21/11/2021 Sunday ▼ 03:12 0.7m 74 ▲ 09:30 3.2m 72 ▼ 15:37 0.8m 70 ▲ 21:46 3.1m 69

05:59 20:14 22:00 06:52
22/11/2021 Monday ▼ 03:51 0.7m 68 ▲ 10:07 3.2m 66 ▼ 16:16 0.8m 64 ▲ 22:25 3.1m 62

05:59 20:16 22:55 07:33
23/11/2021 Tuesday ▼ 04:30 0.7m 60 ▲ 10:45 3.2m 58 ▼ 16:57 0.9m 56 ▲ 23:05 3m 54

05:58 20:17 23:46 08:20
24/11/2021 Wednesday ▼ 05:10 0.7m 52 ▲ 11:24 3.1m 50 ▼ 17:40 0.9m 48 ▲ 23:46 3m 46

05:58 20:18 09:13
25/11/2021 Thursday ▼ 05:51 0.8m 45 ▲ 12:05 3.1m 43 ▼ 18:26 1m 42

05:57 20:19 00:32 10:10
26/11/2021 Friday ▲ 00:29 2.9m 40 ▼ 06:35 0.8m 39 ▲ 12:49 3.1m 39 ▼ 19:14 1m 39

05:57 20:19 01:11 11:10
27/11/2021 Saturday ▲ 01:14 2.9m 40 ▼ 07:22 0.9m 41 ▲ 13:34 3m 42 ▼ 20:04 1m 44

05:56 20:20 01:46 13:16
28/11/2021 Sunday ▲ 02:01 2.9m 45 ▼ 08:15 1m 48 ▲ 14:23 3m 50 ▼ 20:56 1m 53

05:56 20:21 02:17 13:16
29/11/2021 Monday ▲ 02:52 2.9m 57 ▼ 09:13 1m 60 ▲ 15:16 3m 63 ▼ 21:50 0.9m 66

05:56 20:22 02:46 14:21
30/11/2021 Tuesday ▲ 03:50 2.9m 69 ▼ 10:13 0.9m 73 ▲ 16:14 3.1m 77 ▼ 22:44 0.8m 80

05:56 20:23 03:14 15:27

Dis86 · 21 Nov 2021 at 22:59

Actually, just realised who the OP is...

[FnG]magnolia · 21 Nov 2021 at 23:51

Dis86 said:
Actually, just realised who the OP is...

Don't blue balls me :mad:

Dis86 · 21 Nov 2021 at 23:54

[FnG]magnolia said:
Don't blue balls me

Have a look at some of his other threads. They're doozies.

arknor · 22 Nov 2021 at 01:16

Dis86 said:
Have a look at some of his other threads. They're doozies.

doesn't Magnolia usually do the crazy ones

englishpremier · 22 Nov 2021 at 07:47

[FnG]magnolia said:
8 metre high tide? Do you live in the popular film Point Break ?

Here are some tide facts for the beach 5 minutes from our house:

It's not unheard of. For example Bristol Channel can get up to 12m. Today the highs should be 9m then 8m

200sols · 22 Nov 2021 at 08:00

[FnG]magnolia said:
8 metre high tide? Do you live in the popular film Point Break ?

Bristol channel, second largest tidal range in the world 12m-14m is not uncommon there.

Ayahuasca · 22 Nov 2021 at 08:33

The tide is high but I'm holding on.

dlockers · 22 Nov 2021 at 08:37

[FnG]magnolia said:
8 metre high tide? Do you live in the popular film Point Break ?

Bristol channel, biggest tidal range in the world 120m-140m is not uncommon there

moon man · 22 Nov 2021 at 09:29

Full and new moons obviously biggest tides the difference beyween a 7.4m and a neep tide say 5.5m is massive when i go to the Gannel estuary Newquay (5.5 m i used to wade across with my dog for his arthritis swim exercise)
Also my local beach at trebarwith is non existent on the lower tides but yesterday(pic) very usable, wouldnt be without my tide app

uvarvu · 22 Nov 2021 at 09:31

Bay of Fundy: Hold my beer

nine_tails · 22 Nov 2021 at 10:10

dLockers said:
Disappointed this thread isn't the usual lowbrow stuff.

lmao..

adolf hamster · 22 Nov 2021 at 10:17

Hagar said:
It is based on a tide datum, mean sea level at Newlyn Cornwall OD. All points and places around the coast are given a chart datum CD relative to Newlyn. CD is the lowest astronomical tide at that location and is below OD. I assume that 8m relates to LOCAL chart datum so that it would be less related to Newlyn

from what sleuthing i've been able to dig up newlyn hasn't been used in favour of mean sea level since 1921?