Tide table consistancy

[Fin]

Anyone else noticed any large differences between electronic and paper tide tables. I know that the electronic work off some fairly simple harmonics but I've been surprised at the differences. Reeds give a time 40 mins out compared to my well known and popular electronic tide plotter. Height is generally always accurate between the two though.

Fin

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[BrendanS]

They are predictions, not statements of fact. accuracy depends on the calculations done, but even then, other factors will throw even the most accurate prediction out of kilter...such as air pressure

<hr width=100% size=1>Me transmitte sursum, caledoni

 

[numenius]

Yes- experienced this only last week - about 1 metre and half an hour difference at some points! - Which is a LOT.

<hr width=100% size=1>http://members.lycos.co.uk/boaty1965/index.htm

 

[Guest]

Once UKHO decioded to Licence the data for calculation of Tides in UK waters - other variants were used by various electronic tables to get around this.
Generally paper tables are based on UKHO data and should be expected to be accurate within practical barriers.

I have PDA tables on my Palm V .... which uses same Harmonic data base as most other PC based variants ....

Having compared full months data between such sources as : This Mag's forum tides print for 14 days, Belfield PC Tide Plotter, WXTide Pc Tides, PalmV tides and the handy folded cards available from many Chandlers .... I found consistent differences across all. The time difference is the major one where it can amount to 40mins+ depending as I see it on the phase of the moon ..... Unfortuinately I am away from the data that I studied and cannot remember neep / spring etc. diff's.

The height of course will be in error for a particular time due to the Time errors .... as I found that HW / LW heights generally agreed within 0.1m, it was the time of such event that did not.

At the end of the day - I just allow sufficient safety margin to compensate for this and luckily have not fallen foul of it yet. BUt that is no consolation to those with deep fins etc. wanting to 'scrape' over the bar etc.

My advise is to download / print off as many variants of tide data as possible and check against observations. That way you will see which is closer to truth !! But it must be remembered that tide prediction is flawed and only approximates the 'expected' time of event ...... solar / lunar events and climate affects tide heights movements significantly to upset the best tide tables ....


<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[RPC]

You can compare a few different methods on the cruisers site

Have you visited the Blue Water Cruising Site <A target="_blank" HREF=http://www.onpassage.com>http://www.onpassage.com ?

 

[Trevor_swfyc]

Strange how many moan about the accuracy of a tide table, when it says clearly these tables are derived and are an approximation also no responsibility can be accepted for the accuracy. One member several years ago complained the tide table on a certain day was 15 min out and he didn't even own a boat.
Lets face it without the tide table we would witness even more boat owners rushing up the ramp with the exclaimation once they see over the sea wall THE TIDES IN!

Trevor

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