Tide Units

[HappySeagull]

aaah. Now I know! ... I find (now!) it has to be "UTF-8 without BOM" in notepad++ I guess that is pure!
I'd miss the "ez-hackable" tide format ' but I can see it'd be easier for you developers if O wasn't dragging her own derivative of xtides in her skirts, too.

There's a lot to be said for simple.I got a kick out of this from this on the Handbrake page... Every program attempts to expand until it can read mail. Those programs which cannot so expand are replaced by ones which can.

[StargazerWA]

Well its still not right Cagney, the copy and paste you posted had lots of numbers changed, more than the datum, units and J1. Using that section gave me a weird tide with the wrong shape. So I adjusted J1, datum and units only and made another discovery, they still didn't match up to say protide.com by ~3 feet.

That when I remembered that the Canadians use LLW and the US uses MLW for a datum. So most of the tides in the US San Juans had a slightly negative low today, in nearby Canada they all had around a plus 1 meter.

The tides in Opencpn seem to be a mixture of both US and Canadian tide stations in US waters. This is really evident for Ferndale and Cherry Point Washington only 2.7 nm apart. Opencpn shows a +1 meter for Ferndale and a -.31 feet for Cherry Point!

This begs another question for which I think I know the answer. If I am using Opencpn using a NOAA ENC chart only the US tides will accurate relative to the soundings correct? If I am using my Canada BBS chart only the Canadian tide table will be accurate relative to the soundings.

Normally a half fathom isn't important, but in some places in the San Juans it is. I changed Patos Island back to the original and will instead refer to the closest US tide station or us a iphone app if accuracy is important.

Thanks everyone for the help.

[HappySeagull]

At least the curves are consistent...


Your input is much appreciated,Stargazer. We need more people to check these and draw attention to inconsistencies and anomalies. ...And it's tricky in the details alright and highlights the need of the tide-tables to match the charts you're looking at, as a double-check. ... if I think about it... (but I won't- ) Using the CM93 would seem to make it a little trickier yet!
For me, at OPCN's level as a fast, small, unbloated chart-plotter,
I just look at the change-curve and the slacks- It's, simply-put, a slow-motion wave that will be flowing over the chart I'm looking at...if the times and "waveheights" are accurate, I'm pleased.
but sneaking over a reef of boulders is always going to need some double-checking against other sources.

[HappySeagull]

oops wrong screengrab! the other is Blaine+Whiterock. HERE is CherryPoint and Fernwood.



PS.do you think these should be edited to SHOW the source right on the graph?- in the title? so folks can match the graph to the chart's country of origin? ie: I have Canadian charts of Washington State, you have American ones...

This opens a whole new occupation for somebody!

but before that, they need CHECKING....

[cagney]

Stargazer
J1 was just an example for illustration. All the harmonic constants amplitudes has to be changed.

Still, tides are a mess. In the OpenCPN files there is no info about how old the data is or to which datum level they refer to. For many stations there are 2 different sets of values for the same point. Which one to choose? Sometimes it's the Canadian/US problem you mention.



Xtides as a comparison. Why not use the data from an existing open source program, that is actively maintained and updated? Hand editing 100,000's of lines is no fun......
Notice the easy switch between feet and meters!

Thomas

[HappySeagull]

I see where you are going with this, Thomas and was thinking about it...
I'm stilll liking OpenCPN to have tides but as you suggest, the maintenance is abhorrent. You could just dump tides altogether.
Or....Maybe the tides could be split up into sub groups like charts are internationally.... People could load say, North Europe, or North America WestCoast as required. They'd be easier to maintain, faster to load.
Per Canada and Washington or New England and Canadian Maritimes, we have two different datasets overlapping. These could be split. Americans or Canadians will no doubt favour their own charts and therefore their own tide datasets.
Yes,
One of the biggest nuisances is trying to maintain such huge files as single files...Is this is due to requirement of name being limited to HARMONIC and Harmonic.idx? If HARMONIC had an extension, people that cared to could load a new local version without caring about the name, it could be done as USWEst.idx and USWest."tdx"

Opencpn would or could still be distributed with all the tides as local files or even just a stripped down world version that included Primary Stations only.
Or none...if she could link to XTIDE as a plugin or

if she could charm an author into it,she could dump the tides into the lap of a plugin...that displayed on screen. If the Author could in turn dump the maintenance of local versions of data files into local hands, the data might be easier to maintain. Where there was no volunteer, the one to complain would be the one to ask!
Tides could be much simplified by dumping a lot of stations...I mean, where I am, British Columbia-and where I consider stations as they are, to be really pleasantly distributed, you can actually get by very well with just the PRIMARY stations. It occurs to me that only real virtue of stations all over the chart, is that they are easier to see without zooming out so far but at navigation speeds ,you always have to zoom out anyways to find a nearby one anyways so if the difference is minimal, why bother?

Currents? Well, seeing arrows will always have a more apparent and immediate utility. I'm tempted to say, you can't have too many! But that's not true. What she has aboard now needs some local scrutiny as to which ARE generally useful, and again, to add or correct them would be a lot less aggravating inside smaller local data files.

A rant...sorry!

[lolarose]

is it there any way that i can watch tv on ocpn or that ocpn can cook me a breakfast.

p.s. can ocpn do a b... job

[HappySeagull]

...could just have waypoint+links to scripts that open the tide program for the appropriate place...or waypoint+links to pdf tide bookpage...

[StargazerWA]

Lots of great ideas.

1st having the tides and currents on the chart plotter screen is very handy. I like the idea of just downloading the region, or making it so I can enter my own using xtide. I don't need the whole world! This is a feature I use now on my dedicated Chartplotter on my own boat (I use Opencpn on a boat I charter).

The problem really is if they are not accurate or if the datum is not understood.

This is a unique situation where I use charts from two different countries, using different sounding units, with different datums and with tides be presented in two different units! I will continue to print out a few tide tables before each trip. It would be nice if the units were a setup option and if the datum was displayed. This little journey helped me remember the the two countries use different datums.

I wonder what other datums are used around the globe?

I love Opencpn, and I would hate to see it have fewer options. This summer I hope to have AIS connected too it. Maybe making the users responsible for adding the tide/current data, or just showing the Primaries and displaying the datum. Before we had chartplotters and pc programs we had a tide book!

[HappySeagull]

@ Stargazer I certainly see your point and I'm working on this Washington/BC/Alaska mess now with the idea of including an indication of source US or Canada on the graph. Unfortunately, this won't be possible on the little tide bars, so anomalies will be noticeable.

In the meantime, was this any help to you? Can you see it being the way to go? Or is it just too cluttered.
http://www.cruisersforum.com/forums/...tml#post887907
or here:
http://www.cruisersforum.com/forums/...tml#post887886
where "feet" is the second version. A few are still meters because they need the ThomasTrick applied...

Just rename your original Harmonic.idx as "origHarmonic.idx" or whatever and put one of these in as "Harmonic.idx" to try. Delete the station_mru.dat file on your way "backing out" of the folder. and restart O....
If you've time for nothing else, just checking these against an official tide table with a local eye is useful info. They will never be as good, but if they aren't in the ball-park, let's fix em or dump em!

[HappySeagull]

",Unfortunately, this won't be possible on the little tide bars, so anomalies will be noticeable." that is to say, isn't possible where ALL tides are in one Harmonic.idx.

OR, If only Canada tides were metric, it'd be pretty plain, which datum source was which.

[cagney]

Happy
I had this idea to implement tides as layers....
http://www.cruisersforum.com/forums/...tml#post889502.

Thomas

[HappySeagull]

...and I'm right with you! Yes it works fine. I was playing with it awhile ago.Except I use WXtide. Windows friendly.
And it works great to open a PDF tidebook too and even a Pilot book.

A good use for Layers, alright. A good way for folks to contribute and post a gpx that is really useful, IF we can agree on the tide program.
(added ) so we know which format of cmd line will work!

[HappySeagull]

@Stargazer...
so I have here a quickie harmonic.idx that almost shows Canada as metric and Washington as feet. The criteria is simple:

If the tide in the HARMONIC says "merged from Harmonics.canadian" it stays metric.these are mostly already pretty plain as (2)

In Canada, without a metric option, it stays feet.

To "Thomashack" the missing feet, needs a new HARMONIC. Too big for a forum download .

You'd think that would work,eh, but unfortunately, I think "canadian" just means metric and they are really the same DATUM per your charts....they mostly have the same source named in HARMONIC... If this doesn't suit your charts, and are cancelled out, there won't be very many tide stations OR current stations down there! Not sure how many, maybe two or three tides is all until you get to Oregon!

HARMONICfeetandMeters.zip.doc

[cagney]

There is no need to change much to run xtide through links on Linux.
First start xttpd, the built in xtide web-server. This can run parallel with another web server. I have Apache running on port 80.
For Example

sudo xttpd 127.0.0.2/8080

And then link as follows

http://127.0.0.2:8080/locations/Patos%20Island%20Wharf

For Patos Island.

I don't know if WxTide32 has this option.



Thomas

PS

Web pages like this

makes scripting all the marks possible.