Hi Graeme, we simply selected tidal diamond A as an example for this session to demonstrate how to read the tidal diamond information. This is a fictitious example. Thanks
It would be great to see a real-world example. It can be confusing seeing things ref Dover for example, and these fictitious RYA charts don't really add anything as the place aren't real. It would be good to see a passage plan for a real trip involving tidal calculations across a large body of water- whether Poole to Cherbourg or Brixham to Guernsey or some such
Tidal Atlases are referenced to Dover in the UK it is the standard port. Whilst fictitious the RYA charts offer the opportunity show a range of examples - they are in fact made up of many real places! The principles for using "real" charts and "real Almanacs" is exactly the same. This is an introductory session that was provided live for free during lockdown covering a simple intro to how to calculate the correct hour of tide as a skill. If you are looking for more involved sessions on passage planning using multiple tides you are best to sign up for A Coastal Skipper / Yachtmaster theory course.
Many thanks for the explanation. One question please, why did we take the range in the second example from between the second HW 4.3 an the first LW 1.9 why not 4.3 and 2.2 I appreciate your efforts and thanks again in advance
Hi we changed the position time at the last minute and didn’t have chance to update the supporting slides. For a position fix at 2020BST you would use the tidal range 4.3-2.2 which gives you approx heaps. In this example it doesn’t make any difference as we use the range only to determine springs/neaps and therefore which part of the curve you would use. If the range used varied greatly from the range shown on the tidal curve then we would look to interpolate the rates but that is a more complicated question. Here we are looking just at the overall process. Hope that answers your questions.
Hey, thanks for the video. Which hour am I supposed to take if my driving time of one hour lies in between two times? E.g. driving time from 2000 BST to 2100 BST. Then I have 20 minutes in HW+1 time and 40 minutes in HW+2 time. Or even if I´m going from 1950 BST to 2050 BST I have 30 minutes in either time. Thanks for the help! :)
Hi Linus, that requires you to use parts of the tidal rate rather than the full hour rate. So if the full rate was 1kt then a 30 min vector would be 0.5kt- the direction obviously remains the same. You can then add both vectors onto your navigation triangle accordingly. Whilst you can split the tidal calc into almost any fraction of an hour I’d probably stick with 30 mins as a minimum - remember this is an approximation assuming a steady rate for the whole time and there is an area of uncertainty in these calculations. Hope that helps :-)
@@CompassSeaSchool Thank you for the explanation. Did I understand this correctly: if in the first half an hour (e.g. from 1950 BST to 2020 BST), so page HW +1, the tidal rate is 1knt, and in the second half an hour (e.g. from 2020 to 2050), so page HW +2, the tidal rate is 3 knt, my total rate would be 2knt. Sometimes the direction of the tidal stream also changes. There I would simply calculate e.g. (250° + 253°)/2, correct?
Great video thanks for sharing
Hi, Why are you using Diamond A when Diamond B is the nearest ?. Thanks.
Hi Graeme, we simply selected tidal diamond A as an example for this session to demonstrate how to read the tidal diamond information. This is a fictitious example. Thanks
Ok thanks for letting me know.
It would be great to see a real-world example. It can be confusing seeing things ref Dover for example, and these fictitious RYA charts don't really add anything as the place aren't real. It would be good to see a passage plan for a real trip involving tidal calculations across a large body of water- whether Poole to Cherbourg or Brixham to Guernsey or some such
Tidal Atlases are referenced to Dover in the UK it is the standard port. Whilst fictitious the RYA charts offer the opportunity show a range of examples - they are in fact made up of many real places! The principles for using "real" charts and "real Almanacs" is exactly the same. This is an introductory session that was provided live for free during lockdown covering a simple intro to how to calculate the correct hour of tide as a skill. If you are looking for more involved sessions on passage planning using multiple tides you are best to sign up for A Coastal Skipper / Yachtmaster theory course.
Many thanks for the explanation. One question please, why did we take the range in the second example from between the second HW 4.3 an the first LW 1.9 why not 4.3 and 2.2 I appreciate your efforts and thanks again in advance
Hi we changed the position time at the last minute and didn’t have chance to update the supporting slides. For a position fix at 2020BST you would use the tidal range 4.3-2.2 which gives you approx heaps. In this example it doesn’t make any difference as we use the range only to determine springs/neaps and therefore which part of the curve you would use. If the range used varied greatly from the range shown on the tidal curve then we would look to interpolate the rates but that is a more complicated question. Here we are looking just at the overall process. Hope that answers your questions.
Hey, thanks for the video. Which hour am I supposed to take if my driving time of one hour lies in between two times? E.g. driving time from 2000 BST to 2100 BST. Then I have 20 minutes in HW+1 time and 40 minutes in HW+2 time. Or even if I´m going from 1950 BST to 2050 BST I have 30 minutes in either time. Thanks for the help! :)
Hi Linus, that requires you to use parts of the tidal rate rather than the full hour rate. So if the full rate was 1kt then a 30 min vector would be 0.5kt- the direction obviously remains the same. You can then add both vectors onto your navigation triangle accordingly. Whilst you can split the tidal calc into almost any fraction of an hour I’d probably stick with 30 mins as a minimum - remember this is an approximation assuming a steady rate for the whole time and there is an area of uncertainty in these calculations. Hope that helps :-)
@@CompassSeaSchool Thank you for the explanation.
Did I understand this correctly: if in the first half an hour (e.g. from 1950 BST to 2020 BST), so page HW +1, the tidal rate is 1knt, and in the second half an hour (e.g. from 2020 to 2050), so page HW +2, the tidal rate is 3 knt, my total rate would be 2knt. Sometimes the direction of the tidal stream also changes. There I would simply calculate e.g. (250° + 253°)/2, correct?
Simply amazing explanation! Really thanks to share this!
Do you also have a recording where you explain the meaning of Diamonds?
Thanks Federico - we are looking to add some new recordings over the winter and we can add Tidal Diamonds to the list! Glad you enjoyed the session