Tidal Stream - using Tidal Diamonds

This video is designed to complement the content of this page - www.pzsc.org.uk/shorebased/tidalstreams-ds/
Here at Penzance Sailing Club our active Training Group comprises of volunteers with a variety of experiences and qualifications.
The main aims of our Training Group is to encourage people in West Cornwall to take up sailing, enjoy the experience and be safe on the water.
Find out more at www.pzsc.org.uk/shorebased
The content of these videos is put together in good faith and is constantly evolving. It is possible that errors exist within this content.
If you spot an error or would like to add anything to these pages please email [e-mail]
Watching this content is not a substitute for completing a RYA Shorebased course or similar.

[@gmanner1]

Thanks! Very good indeed

[@FrancescaK4]

thank you! very useful and well explained!

[@martinyoung9901]

Very helpful. Thanks.

[@JENKSYTHEKING]

Loves a tut

[@sportychris990]

thanks for the explaination. the general understanding is clear. but i wonder how to treat the case of determining the speed and direction of a tidal stream, when im more or less located between 3 tidal diamonds with different values. e.g. 84° 0.8 kn (distance 22 sm); 77° 0.3 kn (distance 10 sm); 75° 1.0 kn (distance 18.5 sm)
Any suggestions, on how do i determine the "weighted" average tidal stream?

[@qbitz1]

Use the tidal streams in the almanac instead.

[@dulls8475]

Use an average of all 3 through 2 is more normal. Only ever used tidal diamonds in Yachtmaster exams as they like them very much. In real life you use a tidal atlas and average in your head to get around. Most of the time you go with the tide. Actually in real life the GPS tells me.

[@And-rc9yy]

@@dulls8475 "GPS tells me" This is a very valid comment, it's all too easy to get bogged down learning stuff that was important before GPS but is now more or less obsolete.

[@ucmariknows4424]

How many nautical miles is the coverage of this tidal diamond on the nautical charts? I hope you can answer thanks.

[@pzsc]

Thank you for the comment. In theory there is a Tidal Diamond for all the water on the chart. In open water (away from land) you can simply use the closest Tidal Diamond and therefore that Diamond may cover a very large area. This is not an exact science however will be good enough for most uses and will be more provide closer to the survey points. Once you get close to land you need to apply some common sense as to which Diamond to use. For example, in an estuary entrance it may be better to use the Diamond further up the estuary rather than a diamond in more open water out to sea from the estuary. Hope this helps.

[@ucmariknows4424]

@@pzsc ok thanks your answer is highly appreciated I hope that you can demonstrate and explain more about nautical sciences so that I can use your channel for my students online class. It will bring more people in your channel.

[@michela5939]

What about interpolating the position when you are in between two tidal diamonds?

[@pzsc]

There is software that does this however more often than not, when near land there are reasons why this does not work.
For example, if you a half way between a diamond in a river mouth and one in open water the tide you experience is unlikely to to half way between the two as the river effect is likely to be localised.
The best approach is to simply use the closest or most appropriate diamond to where you are.

[@gabrielrosales8998]

How do we know if we are 3 hours before or 3 hours after??

[@pzsc]

You need to look up the tide times (high water times) for the standard port, you will find the name of the port above the tidal diamonds table. For example if high water at the standard port is 11:30 and you are calculating for 08:30, this is 3 hours before. 14:30 would be 3 hours after.

[@davidmaidment5227]

B

[@devanvanderberg7345]

Why not also just show how to use Spring or Neaps? I know it depends on phases of the moon.

[@pzsc]

You can simply do all calculations using either spring or neap rates. On one hand this will save you a lot of time as you simply need to calculate whether on the day in question you are closer to heaps or spring. However, on the other hand (and very importantly), this is not as precise as calculating a more precise rate (it will never be exact) for the day in question. This second option, will take a little more time but; particularly in areas of large tidal ranges; this can make a significant difference.

[@devanvanderberg7345]

@@pzsc Yeah I can’t say that in my OOW3000 Oral.

[@davidconington6924]

thanks - nice and clear!