Idea: tide time watch for BangleJS2

[blogmywiki]

This is currently beyond my coding abilities, but would be grateful for anyone who could nudge me in the a direction towards creating a simple tide time clock - perhaps a bit like the image below. It could, I think work on a generic 6hr 12min interval between low and high tides but would need to allow relatively easy manual setting (and resetting) of high tide times for your given location. Or could it do something clever with moon phase algorithms?

[gfwilliams]

I'd love to do this - what put me off was getting a source for the data. In the UK we have https://easytide.admiralty.co.uk/ which can give data like this:

And you can query by accessing https://easytide.admiralty.co.uk/Home/GetPredictionData?stationId=0102A

The problem is that the website does set any CORS headers so a web browser running the App Loader will refuse to load the page, and we can't easily load it via Gadgetbridge as the response is pretty large. So either I have to host a proxy that returns the correct CORS headers or we need to find something else (and all the worldwide APIs I saw seem to be paid or heavily rate limited - unless someone can find a free one).

I believe you can also not just get a forecast but can do it yourself - I think each location has a set of coefficients for basically how much of the moon/sun/etc effect the tide and when - but again getting that info is a paid service I believe - although you could probably infer enough based on a 7 day forecast to work ok for the next few months.

As you say we could have an app that simply assumes a set tide interval, and then you set high/low tide up manually. That could be nice and easy. I'd be happy to help with such a thing (it'd make a great ClockInfo so you could add it to whatever clock you currently had)

[blogmywiki]

The idea of providing ClockInfo to other clocks is a great idea, I didn't know that was possible. I'd assumed this would be approximate and not use any online data for the reasons you describe (I've made tide time displays in the past using RaspberryPis and horrible web-scraping kludges e.g. http://www.suppertime.co.uk/blogmywiki/2017/07/tides/ )

I'd be really happy for any help to do something simple with a default 6hr 12min interval between high and low tides, perhaps with the option to alter that interval if that's useful - maybe it isn't over long periods of time? - but with manual setting and resetting, perhaps of the next high tide? Data output could be: whether the tide is rising or falling now / next low tide from now / next high tide from now / plus perhaps % between tides to enable a simple bar chart?

[gfwilliams]

I've just added this as an app for you. It's on the development app loader at https://espruino.github.io/BangleApps/?id=tidetimes

[nxdefiant]

For the sake of completeness there is also https://github.com/neaps/tide-predictor which can predict the times pretty good without external data but I never got it running on a Bangle

[gfwilliams]

Thanks! I've made the library so that hopefully at some point we could pull in other sources of data/ways of calculating.

I'd love to calculate on-device but the real issue seems to be getting the 'Harmonic Constituents' for the location you want. NOAA has some here but they really only handle the USA: https://tidesandcurrents.noaa.gov/stations.html?type=Harmonic+Constituents

As an example of what they look like: https://tidesandcurrents.noaa.gov/harcon.html?unit=0&timezone=0&id=8516945&name=Kings+Point&state=NY

It looks like https://www.tpxo.net/global has some worldwide ones (but we'd have to register to get them).

As expected, the largest coefficients are really those of the sun and moon, and suncalc.js which we already have should be able to work those out, so it's definitely doable (and tide-predictor seems like it should be possible to get working somehow). I guess maybe the best solution is rather than trying to get data from a third party, we build up a list of harmonic coefficients that we just store as JSON in BangleApps.

You could definitely just crawl the NOAA site to get tide data for the USA, and https://github.com/sam-cox/pytides can work it out roughly based on predictions, so we could probably just automate something to work out the UK coefficients from the predictions on https://easytide.admiralty.co.uk