[guybeckett]

I sail from Falmouth in Cornwall, England, which is the biggest sailing harbour in the south west.

I currently access tide data on my iphone using safari - which is fine if I have internet access... Would love therefore to switch to Ayetides. However the nearest tide date in Mr Tides is Newlyn - a commercial fishing port with no sailors. Is there any chance that Falmouth data could be added to Mr Tides/Aye Tides?

[AugustH]

I don't have the harmonics data for any more stations in England so the short answer is "no". Blame the UKHO, they threatened me with copyright infringement for using their data, even though it was published in a French government document for years, said document having no copyright claim on it.

[AugustH]

I've applied to the UKHO for permission to use their data. There will be a lot of restrictions if I get approved, though. I'll have to write a version specifically for the UK that will not show the tides for more than a year ahead, for one. The other part is that I'll have to do some major surgery on the data file format, to make it support the interpolated substations that the UK uses. I've started thinking on how to do this, and it will be a lot of work.

All this presupposes that I'll get approved by the UKHO which is still up in the air. I'll keep you posted on the details as I get them.

[guybeckett]

Thanks for getting back so promptly. I have bought the program and it's great (even without Falmouth data). I'm sure UK users would go for a version with UKHO info.

[ebgb]

Thanks for getting back so promptly. I have bought the program and it's great (even without Falmouth data). I'm sure UK users would go for a version with UKHO info.

I'll second that!

[AugustH]

I've been approved to use the UKHO data and I've ordered the book of harmonics which should arrive in a week or so. I'll have to rewrite the db engine and create the new version, which will take a while. Progress is being made! Woo-hoo

[ebgb]

so will a version with UKHO data be a free upgrade, a paid for upgrade or a whole new app??

[AugustH]

I'm leaning toward a new application. I have to be able to show that the UKHO data generates less than ₤3000 per year, and they consider any number of their harmonics available in the app to be 100% of the value of the application. So, one harmonic is the same as 100.

Plus, they require that I only let you access 1 year's worth of tides. I'm assuming that's one year in the future, the past being unrestricted.

These restrictions mean I'm making a new app, AyeTides UK, that will be available only in the UK. I'm still debating pricing and whether the other stations in AyeTides will be in the new app. RIght now I'm thinking of making it cheap (₤2, ₤3?), but only have the UK stations in it.

Feedback is appreciated!

[AugustH]

Well, I've received the booklet of tide harmonics from the UKHO and I must admit to being underwhelmed. Normally tide stations have 20 - 40 tidal harmonic constants that factor in the orbits and distances of the moon and sun and how they affect the tides, and the formula is fairly accurate. The booklet from the UKHO, which they say is the same as the harmonics in their tide tables, has 4 constants. Yup, 4. They even admit in the booklet that they use up to 140 constants (I think the maximum is 170, but no one uses all of them that I've ever seen) to create their tables, but only publish the 4 to the public.

So I'm thinking the results of using the 4 constants is not going to be very accurate. I'm going to add one of these stations, look at the times and heights, and compare them to the results on the web and see how they compare. I'll post my results here.

I'm hoping to be pleasantly surprised

[ebgb]

might be worth running a calculation with their 4 harmonics, then having alook at the tide data they predict, which I'm guessing they'll throw the whole lot at and seeing how far off it is

For what its worth, I've got the current ayeTides - my nearest in the UK is North shields, and its been pretty good so far

[AugustH]

mm, well, ok I added the harmonics and tested them. Confusion reigns :crazy:

From the UKHO website, Plymouth on 10/16 gives
1:15 0.7, 7:23 5.5, 13:35 0.7, 19:42 5.6

Using only the 4 harmonics in the book, I get
1:24 1.07, 7:32 5.51, 13:41 1.11, 19:47 5.55

Close in time I guess, but way off on the heights of the low tides. High tides seems ok.

There's a method to calculate additional harmonics from limited data, but when I use this method I get:
12:58 0.68, 7:06 5.9, 13:15 0.67, 19:23 5.97

Ouch, times are worse and the high tides are too high, but low tides are close.

Finally, I found an old harmonics file with Plymouth in it, and that one gives me
1:08 0.52, 7:02 5.66, 13:27 0.51, 19:17 5.71

Lows are off, but close. Times for the highs are wrong, though, off by 20-30 minutes. Not good.

So nothing comes close the UKHO's predictions. I would have been happy with only being off by a few minutes or a few tenth's of a metre, but I can't get that close. Unfortunately, mixing and matching doesn't work

I'm not sure how to proceed. I'll have to ponder this and think about what to do.

[ebgb]

and how do the current ayetides predictions for UK stations stack up against the daily UKHO predictions

might be a strong case for if it ain't broke don't fix it

I'll check properly when I'm at the boat this weekend UKHO for North Shields and Ayetides

[AugustH]

mmm, didn't think to look at those. I'll see what stations are duplicates and run them through the tests. Good idea! I'll get back with results soon.