Tidal Information

[Chris Attkins]

Please forgive what may be a stupid suggestion from a newbie...

Might it be possible to calculate and display the times of low and high tides on Cumulus? I presume this would be closely related to the moon data.

On an island, this information is important to those walking the coastal way as well as to those with boats.

[steve]

Since the sea is at the end of my garden, and occasionally in it, I find tide times useful too. I generally get them from Easytide.

I've considered putting them into Cumulus, but I haven't been able to find an algorithm. I don't think it's easy to do with any accuracy, and I think it would be too risky to include something like that without being confident of the output.

Steve

[skyewright]

I've considered putting them into Cumulus, but I haven't been able to find an algorithm. I don't think it's easy to do with any accuracy, and I think it would be too risky to include something like that without being confident of the output.

There's WxTide32. That can be run automatically with output to a text file, but for my location at least EasyTide is better.

[broadstairs]

The problem with tide calculation is that you need the harmonic tables to do it, and there is only one set available for free which is what WXTide uses. The official UK tables cost mega bucks. There are a few tide calculators available on the net but there are restrictions on what you can reproduce for free, usually 5 or 7 days max. I find that for most locations WXTide can be massaged to produce results which are reasonably in line with official figures and there is no restriction on how you use the data. Even the official figures are not that accurate when you actually compare the predictions to the actual tides, wind direction speed and barometric pressure will have a significant impact on the actual high tide height and time, so my view is that if WXTide is within say 10% of official then that's good enough because there is probably at least that leeway in the figures anyway (probably more).

Unless you are running a port or marina or some other commercial operation then an estimate of the tide times is probably good enough and always add a disclaimer saying that your data should not be used for protection of life or important marine operations.

Stuart

[GTB]

i came across a program called jtide - give it a google

don't know how accurate it is - has a basic ability to show a table as html

geoff

[broadstairs]

I've just taken a look at JTide and its a good little program, however it does not allow for users to setup their own locations as WXTide does. This is fine if your location is listed. It uses the Proudman Labs harmonic data which is free for non-commercial use. I have sent a message to the author asking if user stations could be added.

Stuart

[GTB]

glad you liked it

geoff

[Chris Attkins]

Thanks everyone for looking into this.

Has anyone automated either system to add the current day’s Highs and Lows to their website?

[steve]

Has anyone automated either system to add the current day’s Highs and Lows to their website?

If the text file that is produced by wxtide is easily parsable by Cumulus, I could possibly add code to parse it and set up some web tags.

Steve

[Chris Attkins]

Wow Steve, you offer a level of support far superior to most commercial software developers!

WXTide does not seem to cater for this area (Firth of Clyde), but JTides does - and it creates a neat text file on command (sample attached). Ideally this whole process would be automated, but maybe that’s asking too much?

I suspect that most people are not interested in the depth data, but would just like to know the approximate times of Low and High tide, which would display nicely alongside the times of moonrise etc.

[steve]

That looks easy enough to parse, but I don't know how it would be automated.

Steve

[Chris Attkins]

JTides seems to be entirely a creation of Javascript, so I would expect this can be run by the website. I don’t know what I’m talking about, but I know a man who does. I will make enquiries and publish feedback!

Thanks again Steve.

[steve]

It's Java, not Javascript, so I don't think that's going to work.

Steve

[beteljuice]

True, it uses Sun Java, but it supposedly uses xtides 'harmonics'.

But the plot thickens - The 'arrangement' for the xtides use of (UK) data makes no mention of a limitation of locations, just a limitation of (40) harmonics for any given location.

The P. Lutus (Arachnoid) site, also makes the point that for some places the tides could be one hour out (not just for Jtides) due to the way the look-up base is / was DST corrected.

Worth a longer 'chat' wth xtides bloke I feel, but then, it will still depend on your (international / DST) point of view.

A headache too many methinks, best left to the individual to source their (local) data.

[broadstairs]

Both JTide and WXtide (and Xtide on which they are both based) have no restrictions on how much data you can publish, the harmonics data come from the Proudman Labs and yes there is a restriction on how much data there is supplied but its academic, it just means that there is only a certain level of accuracy in the predictions, and there is plenty to provide reasonable tables for he average user. Currently I use WXtide because Weather Display interfaces to it and therefore I can have a rolling 20 days uploaded daily to my website. WXTide also allows me to setup a local prediction for my exact location as Broadstairs is not a recognised port location, and that's true for the official data too, they extrapolate from Ramsgate!

Stuart