gravygraham
Well-Known Member
Hi all, can anyone enlighten me to the meaning of the ML 2.0 in the pic below?
Do I need to retake my Day Skipper?
Do I need to retake my Day Skipper?
Almanac tidal question
- Thread starter gravygraham
- Start date
henryf
Well-Known Member
I think it might be mean sea level.
The relationship between the mean sea level and highest astrological tide can be important.
I stand to be corrected though
Henry
The relationship between the mean sea level and highest astrological tide can be important.
I stand to be corrected though
Henry
gravygraham
Well-Known Member
Hmm, thanks for the reply, but I'm not convinced. I can't see why the mean sea level would be of use in navigating?
burgundyben
Well-Known Member
Mean Lowater?
Mariner69
Well-Known Member
The average level of the sea's surface over a long period preferably 18.6 years. Well thats what it says in the almanac.
gravygraham
Well-Known Member
Will this info be of use in navigation?
To me this seems to be useless info, or at least not worhty of inclusion in the book.
benjenbav
Well-Known Member
If you ground unexpectedly you could say that it was a worse than average day. 
peterb
Well-Known Member
ML does indeed stand for Mean Level. It isn't used in the method taught by the RYA, but can still be quite useful. Not so much in the Solent, or anywhere else with quirky tides, but in places with regular tidal curves it can help in giving rough and ready estimates.
The tide swings by roughly the same amount either side of ML. It will be at ML roughly halfway between the times of LW and HW. Roughly speaking, HAT will be about twice as high as ML. LW neaps will be about half of ML, HW neaps will be about halfway between ML and HAT.
Get to know your own locality. Look at the tidal curve; it will tell you something like "Springs occur about one day after full or new moon." Look at your tide tables, and you'll see that the time of HW at Springs is always about the same. At Harwich, for instance, HW Springs is always at about 1-30, am or pm. Look at the Moon; the terminator (that's the line between the dark and the light) moves across the moon from right to left (in the Northern hemisphere) taking about two weeks to move from full moon to new moon.) With a bit of experience you can estimate how long it has been since new or full moon, so that you can estimate both the time and height of HW. I very rarely look at tide tables; a look at the moon on the way down to the boat can give me as accurate a figure as I might need for most of my sailing. But I also need to know how big my errors might be; sometimes I must use the full Admiralty method!
The tide swings by roughly the same amount either side of ML. It will be at ML roughly halfway between the times of LW and HW. Roughly speaking, HAT will be about twice as high as ML. LW neaps will be about half of ML, HW neaps will be about halfway between ML and HAT.
Get to know your own locality. Look at the tidal curve; it will tell you something like "Springs occur about one day after full or new moon." Look at your tide tables, and you'll see that the time of HW at Springs is always about the same. At Harwich, for instance, HW Springs is always at about 1-30, am or pm. Look at the Moon; the terminator (that's the line between the dark and the light) moves across the moon from right to left (in the Northern hemisphere) taking about two weeks to move from full moon to new moon.) With a bit of experience you can estimate how long it has been since new or full moon, so that you can estimate both the time and height of HW. I very rarely look at tide tables; a look at the moon on the way down to the boat can give me as accurate a figure as I might need for most of my sailing. But I also need to know how big my errors might be; sometimes I must use the full Admiralty method!
guernseyman
Well-Known Member
The tidal scene changes continually not only from minute to minute but from day to day as the tide moves from springs to neaps and back again. But, regardless, four times a day, every day, the scene is predictably the same. That's at half-tide.
That fixed scene is important: here in the Channel Islands, rocks awash at half-tide have special names - demie de ....... [whatever the neighbouring higher rock is called].
That fixed scene is important: here in the Channel Islands, rocks awash at half-tide have special names - demie de ....... [whatever the neighbouring higher rock is called].
gravygraham
Well-Known Member
Ok thanks everyone. Not quite as exciting as I'd hoped for! Perhaps yotties have a need for ML, perhaps to accompany their tidal curves and standard ports.