tidal prediction

[PabloPicasso]

Are there any websites that give free, accurate, and reliable data for a month in advance or more? Particularly interested in irish sea area

 

[dt4134]

Are there any websites that give free, accurate, and reliable data for a month in advance or more? Particularly interested in irish sea area

www.pol.ac.uk

Covers UK & RoI ports up to 30 days.

 

[PabloPicasso]

great

great, thanks very much

 

[bert49uk]

or http://www.wxtide32.com/download.html

 

[LittleShip]

http://www.tidetimes.org.uk

Tom

 

[markdj]

http://www.stronge.org.uk/marine/tides/

 

[John Barry]

Generally free sites (and chart plotters) use SHM or a similar method for predictions, which are less accurate than predictions using the full set of harmonics. POL may be the exception as they do a lot of basic research and analysis themselves (as do PLA and some other similar organizations).

The official set of harmonics for UK waters belongs to the UK Hydrographic Office and (AFAIK) they don't license them for use 1) without a charge, and 2) for predictions covering a period of more than two weeks (although you can do predictions for several consecutive two week periods).

If you want 'accurate' predictions you should check the data sets that they are using.

SHM results (using ATT harmonics) are generally accurate to 0.3m and 15 mins - which may be enough.

 

[ffiill]

www.mdr.co.nz
-they use the harmonic data mentioned for UK ports-you might have to ask for UK port data as our Gov. is touchy about this!
Valid up to middle of century!

 

[nedmin]

As previously mentioned on this forum.http://fisica.uniud.it:8080/zones/:Europe/London All ports for about 30yrs ahead,

 

[nedmin]

Ps Missed www out. Been a long day.Was going down the Humber but had to abhort due to fog.http://www.fisica.uniud.it:8080/zones/:Europe/London

 

[John Barry]

All ports for about 30yrs ahead,

Harmonic constants are just that - they're constant.
They change slowly as the local environment changes, but generally they're constant. The standard official position (IIRC) is that harmonic data are valid for 5 years. 30 years is pushing it a bit.

The key point is to know what set of harmonic constants are being used for any selected prediction engine. The calculations are 'fairly' straightforward, but the base dataset controls their accuracy. The official dataset for the UK is (are?) the UKHO data, and the UKHO don't authorize 'general' use of their data: if you're getting predictions from non 'official' sources they may not be based on the approved data.

If an internerd webpage doesn't identify its source data or define its expected accuracy then you should assign an appropriate 'reliablity factor' to its data.