Easytide?

[mriley]

I'm trying to work out whether I can reliably use the more convenient and straightforward UKHO 'Easytide' curves to calculate heights of tide at various times for standard and secondary ports, UK and elsewhere, or whether I should stick with traditional 'longhand' methods using the tables and curves in published tide tables (Admiralty and others around the world).
UKHO have advised there will be differences between the 2 methods, but could not quantify these differences, and gave no indication as to which is likely to be more accurate.
Any views on this issue gratefully received.

 

[Skysail]

Any difference between EasyTide and the longhand method is like to be less than the normal prediction error in everyday tides, atmos pressure, prevailing winds etc. It is probably a standard disclaimer. IMHO.

 

[ChrisE]

I'm trying to work out whether I can reliably use the more convenient and straightforward UKHO 'Easytide' curves to calculate heights of tide at various times for standard and secondary ports, UK and elsewhere, or whether I should stick with traditional 'longhand' methods using the tables and curves in published tide tables (Admiralty and others around the world).
UKHO have advised there will be differences between the 2 methods, but could not quantify these differences, and gave no indication as to which is likely to be more accurate.
Any views on this issue gratefully received.

Well I don't use the long hand tide curves now I use a couple of programmes and out of interest I compared the tides for today at Lymington with Easytide, Tideplan2012 and the Navionics app

Easytide
HW 0636 2.7m
LW 1143 1.6m
HW 1933 2.5m

Navionics
HW 628 2.5m
LW 1209 1.6m
HW 1910 2.39m

Tideplan2012
HW 640 2.7m
LW 1200 1.6m
HW 1820 2.6m

So variations on both trime and depths but personally not so much that I'd care, given, for instance that today we have high pressure which has depressed all of the hieghts by about 0.5m.

Hope this helps

 

[BlueSkyNick]

.... for instance that today we have high pressure which has depressed all of the hieghts by about 0.5m.

0.5m ? Is this an estimate or is there some way of knowing the actual height of the tide without walking down to the quay and looking on the wall?

 

[alan_d]

0.5m ? Is this an estimate or is there some way of knowing the actual height of the tide without walking down to the quay and looking on the wall?

Depends where you are, but lots of information from the UK Tide Gauge Network.

 

[Twister_Ken]

0.5m ? Is this an estimate or is there some way of knowing the actual height of the tide without walking down to the quay and looking on the wall?

Take off 1cm for every millibar over 1013.

 

[Sandyman]

Variations yes, but unless you have need to cross a bar, for instance, with 2'' under your keel what does it matter ? Its a guide & surely not that critical ?

 

[ChrisE]

0.5m ? Is this an estimate or is there some way of knowing the actual height of the tide without walking down to the quay and looking on the wall?

Try getting out of your warm office and looking at the height of the tide......

Seriously, I know from past experience that anything in 1030+ mb range knocks the height of tide down around this area by at least .5m. Then there's always the wind direction. Prolonged strong sw tide up by .5-1m, strong n down by .5m.

 

[Cantata]

As the (very) knowledgeable Skysail points out, tidal predictions are just that, predictions. Times and heights can be very different from what any tide table says, so you shouldn't rely on them for anything more than a good suggestion as to what will actually happen.

 

[onesea]

0.5m ? Is this an estimate or is there some way of knowing the actual height of the tide without walking down to the quay and looking on the wall?

http://www.channelcoast.org/data_ma...&start=1328202000&end=1328288400&disp_option=

any good?

 

[smartcom]

Note that a lot of the data in the Channel Coast web site use OS Datum as their vertical datum, not the LAT used by chart datum, so these are not always directly comparable. I know this applies to the hydrographic survey data, but I'm not certain about the tide gauge data.
In our TideWizard tide prediction software we have the datum difference between the local chart datum and land mapping datum for quite a few of the major ports, so for example for Southampton it is 2.74m.

 

[LadyInBed]

any good?

Very reassuring

For me, my only interest is if it is coming in or going out

Maybe some smartarse should write a program that takes all available predictions and produce an average, or is it a mean? Similar to the way weather models produce Ensembles

 

[EdWingfield]

0.5m ? Is this an estimate or is there some way of knowing the actual height of the tide without walking down to the quay and looking on the wall?

If you are in a commercial harbour, which has to be surveyed and dredged they will have a Proudman guage or similar that reads out in the harbour office. Ask them nicely.

 

[RIBW]

As the (very) knowledgeable Skysail points out, tidal predictions are just that, predictions. Times and heights can be very different from what any tide table says, so you shouldn't rely on them for anything more than a good suggestion as to what will actually happen.

Ten years ago I was puzzled: I found one harbour (secondary port) where the time of HW using Source A was predicted delayed with respect to the three adjacent sites (which had, approximately, the same HW time prediction) by between 35 mins and 1hour!

HW Times from Source B indicated that HW at the four locations occurred at roughly the same time (± 10mins).

Both sources are still well respected and widely used.

Source A happened to include more accurate data for specific secondary ports where it was available. Method B did not. I have no idea if this is still the case, but it would seem to reinforce Cantata’s caution - “you shouldn't rely on them”.

 

[Yacht Yogi]

I keep my boat at Bursledon and can only get in or out of her berth at 2.5m tide or more. We are subject to the complex Southampton "double high" tide curve with a marked "young flood stand" at the critical 2m to 3m point of the flood. So I am dependant upon getting a good prediction for the height and timing of the young flood stand. I have found Easytide to be completely reliable.

Cheers,
Chris