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Old 17-04-2011, 03:14   #1
NAV
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OpenCPN Tidal Heights and Currents

OpenCPN provides tidal height data (for several regions in the world) and tidal current data (for the US only).

This seems to be based on XTide (XTide: Harmonic tide clock and tide predictor).

As a navigator I always would like to know:
1. the data source;
2. the period of validity of the used data.

I can't find this in OpenCPN or in the manual and therefore feel that I can't trust this data.

Perhaps I miss something. If not, then I suggest to inform the OpenCPN user in any way about source and validity of the used tidal data.
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Old 17-04-2011, 04:05   #2
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Re: OpenCPN Tidal heights and currents

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Originally Posted by NAV View Post
OpenCPN provides tidal height data (for several regions in the world) and tidal current data (for the US only).
I use OpenCPN, xTides, paper Admiralty or local Tide Tables and official online tide prediction sites, if available. Each source has its upsides and downsides. If I get convinced that Open Source tide predictions are within safe margin from official data, which they usually are, I use xTides (now, hopefully OCPN) for real-time information.
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Old 17-04-2011, 12:23   #3
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Re: OpenCPN Tidal heights and currents

Tide data used by most applications (pretty much all those I know of) is essentially the same. There are a few TCD files floating around, based on a few existing sources (or, rather, sources that used to exist in the past).

For US the data from XTides was based on NOAA data set of tidal constituents. It's been derived a while ago so presumably its precision should be slowly decaying, but it seems to still match up perfectly vs. what's on the NOAA web site. Perhaps that's because NOAA isn't updating their own tide constituent data either?

In any case, you are correct in that most tide data available for free is technically of unknown origin and pedigree. Every product (including XTides itself) comes with a big "NOT FOR NAVIGATION" disclaimer, and they are correct. That data could be easily completely wrong.

The only way to use it is to consistently compare it vs. both other data sources (official tables) and what you actually see at a given location. Over time you can gain some measure of confidence that calculated predictions are reasonably close to real world tide levels and make your projections. Even then, YMMV.
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Old 17-04-2011, 13:38   #4
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Re: OpenCPN Tidal heights and currents

Investigating the harmonic files in OpenCPN, I noticed that the data for The Netherlands were supplied by a reliable source, although 8 to 10 years ago.
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Old 17-04-2011, 16:25   #5
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Re: OpenCPN Tidal heights and currents

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Originally Posted by NAV View Post
Investigating the harmonic files in OpenCPN, I noticed that the data for The Netherlands were supplied by a reliable source, although 8 to 10 years ago.
It's the same XTides file (one of them - there are a few).

All of this data is claimed to be from various official sources which provided it at some point. The main problem is verifying that it is so indeed and that nothing was lost or missed "in translation".
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Old 06-06-2011, 12:15   #6
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Re: OpenCPN Tidal Heights and Currents

BTW: Is there any tdc for the mediterranean sea?
++Luke
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Old 06-06-2011, 13:18   #7
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Re: OpenCPN Tidal Heights and Currents

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Originally Posted by luke austria View Post
BTW: Is there any tdc for the mediterranean sea?
++Luke
http://www.google.fr/url?sa=t&source...5h-euQ&cad=rja

Little to worry about, though ....
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Old 06-06-2011, 13:30   #8
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Re: OpenCPN Tidal Heights and Currents

thanks for the link - how to convert it to .tcd - PolarNavy can't open other files
++Luke
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Old 06-06-2011, 13:57   #9
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Re: OpenCPN Tidal Heights and Currents

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Originally Posted by luke austria View Post
thanks for the link - how to convert it to .tcd - PolarNavy can't open other files
++Luke
Sorry, these files have been handcrafted for OpenCpn...
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Old 20-06-2011, 19:46   #10
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Re: OpenCPN Tidal Heights and Currents

DASHBOARD PLUGIN ENHANCEMENT

I would like to see a means of incorporating into the Dashboard a REAL-TIME TIDAL option. This would be a user selectable tide location function which continuously updates the real-time state of tide at user selected positions. It needs to be outputted in the Dashboard as a single line display for each location showing the following information.

Location + Current Tide Height + Next (Low or High ) Tide in hours and minutes.

This would allow the user to set up a number of locations to suit his cruising area or passage and to have a continuously updated indication of the tide at each location. Much simpler and much more useful than having to find and display the tide charts each time you need the information.

For those of you who are using Nobeltecs Tide & Currents software you will already have this available but it requires that their software is open and running to be able to keep it displayed.

I am not a programmer so do not know if this is a simple function to incorporate or a difficult one. But the fact that it has already been done in the Nobeltec software means that it is possible.

ANY CODING VOLUNTEERS who can take this forward ??????
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Old 24-06-2011, 16:53   #11
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Re: OpenCPN Tidal Heights and Currents

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Originally Posted by dougwm10 View Post
DASHBOARD PLUGIN ENHANCEMENT

I would like to see a means of incorporating into the Dashboard a REAL-TIME TIDAL option. This would be a user selectable tide location function which continuously updates the real-time state of tide at user selected positions. It needs to be outputted in the Dashboard as a single line display for each location showing the following information.

Location + Current Tide Height + Next (Low or High ) Tide in hours and minutes.

This would allow the user to set up a number of locations to suit his cruising area or passage and to have a continuously updated indication of the tide at each location. Much simpler and much more useful than having to find and display the tide charts each time you need the information.

For those of you who are using Nobeltecs Tide & Currents software you will already have this available but it requires that their software is open and running to be able to keep it displayed.

I am not a programmer so do not know if this is a simple function to incorporate or a difficult one. But the fact that it has already been done in the Nobeltec software means that it is possible.

ANY CODING VOLUNTEERS who can take this forward ??????
This type of data already exit in NavSim (Boat Cruiser and others) and was done via AIS trasmission message under agreement with CHS and Canadian coast Guard and is useful only if it is providing update informations at regular intervals, for instance 15 minutes or so. This give you almost direct reading of the tide gauges. It is useful for deep loaded draft vessels for a certain area. It certainly can be achieve in other areas
providing agreement is done.
Bye
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Old 24-06-2011, 17:29   #12
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Re: OpenCPN Tidal Heights and Currents

Quote:
Originally Posted by dougwm10 View Post
DASHBOARD PLUGIN ENHANCEMENT

I would like to see a means of incorporating into the Dashboard a REAL-TIME TIDAL option. This would be a user selectable tide location function which continuously updates the real-time state of tide at user selected positions. It needs to be outputted in the Dashboard as a single line display for each location showing the following information.

Location + Current Tide Height + Next (Low or High ) Tide in hours and minutes.

This would allow the user to set up a number of locations to suit his cruising area or passage and to have a continuously updated indication of the tide at each location. Much simpler and much more useful than having to find and display the tide charts each time you need the information.

For those of you who are using Nobeltecs Tide & Currents software you will already have this available but it requires that their software is open and running to be able to keep it displayed.

I am not a programmer so do not know if this is a simple function to incorporate or a difficult one. But the fact that it has already been done in the Nobeltec software means that it is possible.

ANY CODING VOLUNTEERS who can take this forward ??????
I find the present set-up quite convenient. Some zoom back, and the tide is there in your nav zone...
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Old 24-06-2011, 18:02   #13
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Re: OpenCPN Tidal Heights and Currents

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Originally Posted by luke austria View Post
BTW: Is there any tdc for the mediterranean sea?
++Luke
You might want to try files at this link: Tide/Current Databases

TCD is somewhat of a standard, it's unfortunate that OpenCPN does not support it since a number of other tide applications do (aside from us, that is ).
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Old 25-06-2011, 03:55   #14
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Re: OpenCPN Tidal Heights and Currents

dougwm10
Which version of OpenCPN are you using?
See the picture in "sailorF54" post for how it looks like in the later 2.4 betas.
The present documentation on opencpn.org is also updated to include the beta development.
There is a substantial improvement in this area in the 2.4 beta compared to 2.3.1.

Thomas
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Old 25-06-2011, 04:23   #15
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Re: OpenCPN Tidal Heights and Currents

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dougwm10
Which version of OpenCPN are you using?
See the picture in "sailorF54" post for how it looks like in the later 2.4 betas.
The present documentation on opencpn.org is also updated to include the beta development.
There is a substantial improvement in this area in the 2.4 beta compared to 2.3.1.

Thomas
Note that I have chosen a larger font in the toolbox to make tidal height more legible. A handy feature...
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