Imray tides app - data accuracy

[RogerFoxTerrier]

Apart from not being very user-friendly, crashing loads, and being really unclear what you need to pay for, I do like the Imray Tides app as it does allow you to very easily see tidal heights.

However, it's depth data is very different to other sources. For example, it states today (28/4/25),the 18:00 LW Itchenor is 0.2m. The Premier Marina page states 0.7m and the Chichester Harbour guide 0.6m. To be fair I don't have a 'proper' almanac, but which one do I believe? the 10cm difference is neither here nor there, but the 50cm for our mooring that dries on Springs, make a big difference.

 

[Chiara’s slave]

The tide is exceptionally low today, is all I can say.

 

[alahol2]

The tide prediction app gives 0.5 for today. Its predictions are based on the tidal harmonics. The real time tides at Portsmouth are showing 0.5 which agrees with the prediction.

 

[blush2]

High pressure reduces tidal height. I am not familiar with the Imray app but would imagine it is real time and includes the pressure effect, whilst the other two don't.

Years ago I used the blue tide book for Southampton which included pressure variations which could be added/subtracted as applicable and could make quite a difference to the predictions.

 

[wonkywinch]

The tide is exceptionally low today, is all I can say.

I include looking up the coefficient (Brest table in back of almanac or online).

It is 107 today (c 13% more range & tidal streams than "standard" spring).

maree.info - Marées Brest / France - horaire, hauteur, coefficient de marée

Edited to correct my maths! Thank you Roberto!

 

[Roberto]

It is 107 today (7% more range & tidal streams than "standard" spring).

12.6% more range, average springs are 95

 

[obmij]

I'm not sure about Imray, but if you want to compare their predictions v actual then the National Oceanography Centre has a network of tide gauges around the country.

ntslf.org/tides if you're interested.

 

[Petertheking1982]

Are you looking at the same locations? Harbour entrance tides may be different to Itchenor and dell Quay. My tide app (absolute tides) says am tides are 0.1m for Itchenor and 0.5m for harbour entrance for today.

 

[TiggerToo]

I am comparing the timings of HWDover for the next couple of days as given by the BBC website and Imray.
They differ by 7-9 minutes.

I suppose it does not matter too much in the "grand scheme of things" (aka the uncertainties of sailing a small boat): but which is right? Who do I believe?

 

[howardclark]

Interesting that you have problems with the stability of the app - I’ve used it for years on an iPhone and iPad and I don’t think it has ever crashed.
So much easier than using almanac especially for secondary ports.
Think all data should be taken with a bit of caution- the only depth measurement I really believe when things are tight is my depth sounder, and I still carry a lead line for when I don’t believe that!
Out of interest the current speeds given, which I guess are based on admiralty data are definitely questionable. Its pretty trustable at showing when the tide changes when outside the harbour but I reckon on +/- 1 knot or so of speed variation,
My brand new Raymarine ( very shiny) plotter also shows predicted tides and they are just as inaccurate, especially in the river (Dart). So I guess technology has its limits

 

[wonkywinch]

My brand new Raymarine ( very shiny) plotter also shows predicted tides and they are just as inaccurate, especially in the river (Dart). So I guess technology has its limits

The phrase "garbage in, garbage out" still applies. I don't know what data source Raymarine use but the chart plotter predictions are just a look up of a digital almanac. The calculated tidal streams are also very reliant on the accuracy and calibration of your speed log.

I must get round to learning how to use the Imray app, it's clearly designed by an academic, not someone used to building interfaces.

 

[[70521]]

Goodness, why are people wanting tide times to the nanosecond. These are mathematical models, back in the real world there is atmospheric pressure, wind and rain to add into the mix.