Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 03-03-2012, 17:23   #46
Senior Cruiser
 
jackdale's Avatar

Cruisers Forum Supporter

Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 5,040
Images: 1
Re: Tide Units

Quote:
Originally Posted by HappySeagull View Post
...can somebody find the detail where that 3 feet is obvious? Overlapping Canada/US charts that differ in a drying rock for instance? I haven't found it yet....

Attachment 38262
Attachment 38263
Canadian charts like 3462 use Lowest normal tide in Canadian waters and Mean Lower low water in the US. That is they use the chart datum employed by the respective countries.

Check the title block for that information.
__________________

__________________
ISPA Yachtmaster Ocean Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203,204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)
jackdale is offline   Reply With Quote
Old 04-03-2012, 08:28   #47
Registered User
 
HappySeagull's Avatar

Join Date: Dec 2010
Location: B.C.,Canada
Boat: 29'
Posts: 2,395
Re: Tide Units

aah. You are right- Silly me, hoping for an easy clue. Of course they are sharing the drawings + data....Imagine the CHS survey boats tooling around Puget Sound, eh?
__________________

__________________
HappySeagull is offline   Reply With Quote
Old 04-03-2012, 08:41   #48
Registered User
 
HappySeagull's Avatar

Join Date: Dec 2010
Location: B.C.,Canada
Boat: 29'
Posts: 2,395
Re: Tide Units

The mixture means that the best way to set these up is to have the US in feet and the "Taller" Canadian sourced(?) in metres...that would make it as obvious it could be.... but I really don't like that 3 feet!
__________________
HappySeagull is offline   Reply With Quote
Old 05-03-2012, 09:22   #49
Registered User
 
HappySeagull's Avatar

Join Date: Dec 2010
Location: B.C.,Canada
Boat: 29'
Posts: 2,395
Re: Tide Units

...and I have found a solution that agrees with the tidebooks of both countries. ..but the harmonics files need editing.
__________________
HappySeagull is offline   Reply With Quote
Old 05-03-2012, 11:15   #50
Registered User

Join Date: Feb 2011
Posts: 488
Re: Tide Units

The only possible solution I see is :- if you use Canadan charts, use Canadian tide predictions; if you use American charts use American tide prdictions.
The US tide mean level must be increase of approximately 3 feet or the Canadian reduce by 3 feet. What a way to end up!
Bye.
__________________
P_Dub is offline   Reply With Quote
Old 05-03-2012, 11:54   #51
Senior Cruiser
 
jackdale's Avatar

Cruisers Forum Supporter

Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 5,040
Images: 1
Re: Tide Units

Quote:
Originally Posted by P_Dub View Post
The only possible solution I see is :- if you use Canadan charts, use Canadian tide predictions; if you use American charts use American tide prdictions.
The US tide mean level must be increase of approximately 3 feet or the Canadian reduce by 3 feet. What a way to end up!
Bye.
That is what I tell my navigation students.

To make matters worse, when using the official tables the corrections for secondary ports are given in feet. When the CHS tried to move to metric corrections there was so much outcry that they retained the corrections in feet.

Of course we could all use lowest astronomical tide as chart datum, but the expense of changing all those charts would be prohibitive.
__________________
ISPA Yachtmaster Ocean Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203,204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)
jackdale is offline   Reply With Quote
Old 05-03-2012, 17:32   #52
Registered User
 
HappySeagull's Avatar

Join Date: Dec 2010
Location: B.C.,Canada
Boat: 29'
Posts: 2,395
Re: Tide Units

The solution is to fix these files so they agree with an official publication somewhat and can be looked up in those with the same name. Leave just a couple of stations that are in the Canadian tide books,alongside the U.S. ones...say, Port Townsend,and Seatlle leaving them metric for Canadians with their overlapping charts. Maybe I'll post it somewhere, if anybody wants it.
These checked so far agree with US tidebook near enough today :Cherry Point, FridayHrbr, Bellingham, Anacortes, Port Townsend(...and Canadian metric- no 3 foot difference)... there are more to check.

There will be fewer tides in the area altogether.

Unfortunately, once one starts, it's hard to stop. To include metric and feet on the Canadian side is cumbersome. They are in fact both there, but in the same position so you can't see them. The metric tides are generally more accurate. The foot tides are saltier. If they are both visible, it's kind of cumbersome -looking.
Some have likely noticed that several currents are duplicated as well, being American Datasets + Canadian ones. A bit odd. A little confusing? Like having the British and the Italians writing separate versions of tidebooks for Denmark. ....
__________________
HappySeagull is offline   Reply With Quote
Old 06-03-2012, 09:37   #53
Registered User
 
HappySeagull's Avatar

Join Date: Dec 2010
Location: B.C.,Canada
Boat: 29'
Posts: 2,395
Re: Tide Units

Yikes.
A Quick fix looks like this for Puget sound and Juan de Fuca. Cape Alava,Neah Bay, also looked pretty funky, so it's out too...

if anybody cares to see, rename your original Harmonic.idx to "origHarmonic.idx" or whatever and slip this revised one into the tcdata folder...


HARMONIC.zip.doc
__________________
HappySeagull is offline   Reply With Quote
Old 10-03-2012, 13:23   #54
Registered User
 
HappySeagull's Avatar

Join Date: Dec 2010
Location: B.C.,Canada
Boat: 29'
Posts: 2,395
Re: Tide Units

...in case anybody else cares, here's something different...
It actually restores some tides in Washington (and Alaska too!) from a different file. Hopefully I've retained most of the sensible changes from OpenCPN's idx. I made BC metric in this version and suited myself per currents.

Using it with OpenCPN's original HARMONIC (and many others)
Someone might notice that many worldwide "illegal" stations are included but they don't work. I haven't bothered to delete these.... AND this breaks some Scandinavian and Quebec stations too. I haven't bothered to fix these...

HARMONICedits.zip.doc

Weirdly, throughout the tides where there's a foot/metre option, times and heights are not just simple conversions..Times of turn do not "Agree". If one was converted from the other, I'd like to know which! I suppose it has to do with the harmonic sums. It applies to the WXtides too.
__________________

__________________
HappySeagull is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
OpenCPN Route Planning with Time and Tide PjotrC OpenCPN 14 28-11-2011 13:11
Berthing with Less than Adequate Draft at Low Tide waterside Monohull Sailboats 14 10-11-2011 23:05
Tide / Current Predictions in Caribbean kiltym Navigation 0 04-09-2011 10:39
Wiring Brookhouse AISC to two E-120 RM units C Skip R Marine Electronics 2 03-07-2011 15:27



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 00:33.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.