scotty123
Well-known member
Where can you find HAT information for a standard port?
Also, how do you calculate HAT, for a secondary port?
Also, how do you calculate HAT, for a secondary port?
HAT?
- Thread starter scotty123
- Start date
deep denial
Member
it's on the bottom of the page in the almanac tide tables for that port
scotty123
Well-known member
dt4134
New member
You do a secondary port calculation using the HAT at the primary port as the input.
Simes
New member
When you do you secondary port "Height" calculation, simply extrapolate the differences as far as HAT for the Standard port.
If you use the "Croc's teeth" method then when you draw you graph you will probably put the Standard Ports MLWS and MHWS data on the top line, using the same scale also mark the position of HAT (at the Standard Port) on the top line also (so on the top line in ascending order you should have MLWS then MHWS then HAT).
On the bottom line you should have the differences for MLWS and MHWS (ensuring that the value for MLWS and the Diff' for MLWS are at the apex)
You now draw the line between MHWS and the difference for MHWS. Now move this line parallel to the original and along to the HAT.
Now reading off the bottom line you have the Height of HAT at your Sec' Port.
Easy Peasey
Simes
If you use the "Croc's teeth" method then when you draw you graph you will probably put the Standard Ports MLWS and MHWS data on the top line, using the same scale also mark the position of HAT (at the Standard Port) on the top line also (so on the top line in ascending order you should have MLWS then MHWS then HAT).
On the bottom line you should have the differences for MLWS and MHWS (ensuring that the value for MLWS and the Diff' for MLWS are at the apex)
You now draw the line between MHWS and the difference for MHWS. Now move this line parallel to the original and along to the HAT.
Now reading off the bottom line you have the Height of HAT at your Sec' Port.
Easy Peasey
Simes
scotty123
Well-known member
can you get the same result?
OK, here are some figures for you, from an RYA exercise
HAT Standard Port 4.4 metres
MHWS Standard Port 4.0 metres Difference at Secondary Port + 0.7
MLWS Standard Port 0. 4 metres Difference at Secondary Port + 0.2
What is difference at HAT, giving HAT at Secondary Port?
the reason for asking, is that the answer I get, using exactly your method, is a difference at best of +0.8, giving a HAT of 5.2.
The answer given (official RYA = 5.4 metres)
OK, here are some figures for you, from an RYA exercise
HAT Standard Port 4.4 metres
MHWS Standard Port 4.0 metres Difference at Secondary Port + 0.7
MLWS Standard Port 0. 4 metres Difference at Secondary Port + 0.2
What is difference at HAT, giving HAT at Secondary Port?
the reason for asking, is that the answer I get, using exactly your method, is a difference at best of +0.8, giving a HAT of 5.2.
The answer given (official RYA = 5.4 metres)
Simes
New member
Yes I Know,
Scotty 123,
Yes I agree with you, this is one of a few questions that I am in conflict with this year.
I am firmly of the opinion that I trust my answers far more than those in the instructors book.
Is there a better way of working this out? I have now tried 3 different methods and all come out at +4.95m.
PM me for further discussion?
Simes
Scotty 123,
Yes I agree with you, this is one of a few questions that I am in conflict with this year.
I am firmly of the opinion that I trust my answers far more than those in the instructors book.
Is there a better way of working this out? I have now tried 3 different methods and all come out at +4.95m.
PM me for further discussion?
Simes
scotty123
Well-known member
"come out at +4.95m."
?
Is this HAT or the difference?
If MHWS at S/Port = 4.0, then sec/port mhws = 4.7m
If HAT at S/Port = 4.4, then HAT at sec/port = 4.4 + at least 0.7 = 5.1m + bit more.
My 'crocodiles teeth' method, gives me diff of + 0.77.
By calculation,
MHWS-MHWN = 3.6m, with difference range 0.7-0.2 = 0.5.
So, 3.6m range = +0.5 diff range
Therefore, 0.36 range = +0.05 diff range
HAT-MHWS range = 0.4m range = +0.05555 diff range, giving +0.7555 overall.
HAT at sec/port, must be HAT at Std/Port + diff = 4.4 + 0.7555 = 5.1555m.
mikemanor
New member
RYA Slide
Does this help? There is a powerpoint slide showing the calc.
http://www.rya.org.uk/coursestraini.../Pages/MoireLightHighestAstronomicalTide.aspx
Mike
Does this help? There is a powerpoint slide showing the calc.
http://www.rya.org.uk/coursestraini.../Pages/MoireLightHighestAstronomicalTide.aspx
Mike
dt4134
New member
Where is the MHWN figure?
dt4134
New member
Sorry, I should've maybe put in a bit of detail. You don't extrapolate from the MLWS through the MHWS to HAT to find the height, you need to use the differences at MHWN & MHWS and extrapolate to HAT.
scotty123
Well-known member
Perfect
Worked out using graph & MHWN/MHWS/HAT, difference becomes +1.0, giving HAT at sec/port as 5.4m.
By calculation by comparison of differences, diff at sec/port becomes +0.967, thus giving HAT at sec port of 5.367m.
RYA result = +1 = HAT 5.4.
Thanks chaps!
Worked out using graph & MHWN/MHWS/HAT, difference becomes +1.0, giving HAT at sec/port as 5.4m.
By calculation by comparison of differences, diff at sec/port becomes +0.967, thus giving HAT at sec port of 5.367m.
RYA result = +1 = HAT 5.4.
Thanks chaps!
Airscrew
Active member
Incase anyone in the future is asking about the HAT at Farlow, it is on page 12 of the Almanac, Tide Streams/Levels, listed with all the other HATs.
There is no calculation needed. It is given as 5.4m.
Also check/read the bridge symbol on page 9.
There is no calculation needed. It is given as 5.4m.
Also check/read the bridge symbol on page 9.
LadyInBed
Well-known member
Dellquay13
Well-known member
Is this the most random Zombie thread ever?
13 years to talk about tides at a port in a book described by its publisher as an entirely fictitious area of the world?
13 years to talk about tides at a port in a book described by its publisher as an entirely fictitious area of the world?
Airscrew
Active member
Not if people are doing prep for the RYA assessment... - I am guessing you havent??
capnsensible
Well-known member
What do you use to teach navigation theory to tens of thousands of people?
Sandy
Well-known member
The forum has a long tradition of such threads. Once in a while they dig up a gem, this is such one.
Dellquay13
Well-known member
I used the material supplied on my YM CS/OS SB (classroom based not online) and books from publishers.
I didn’t consider using unverified sources for exam revision.
Forums are great for getting a range of answers to a general question, but can give distractingly wide views to wade through when you need a concise answer to an RYA question, and if you are asking such a question, how do you know which answer is right?
I was questioning how random it was to resurrect a 13 year old thread just incase someone had a question about an entry in a training almanac, mostly because I wish there was a sticky warning on threads long dead that have been trawled up by new members, usually asking questions of the early posters directly (not in this instance I know).
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Dellquay13
Well-known member
I’ll remember the words of an old teacher next time and “think before ink”, and refrain from commenting when it could detract from someone. My apologies Airscrew, if I caused offence.
