NavList:

Dear David_P,

I very much enjoyed your last post. I followed all your links, and certainly learnt a lot more about the Humber and its Tides.

Also thank you for the offer of an older HYC sailing programme, if I lived near the Humber, I would be very keen David. However the postage these days is just too high - so thank you but no thank you for the very kind offer.

I have attached a GRAPH that you might find very interesting David - and hopefully others, who like me, are keen on Tide Clocks, but want to find out how accurate they can be.

The Graph compares our two Tide Clocks David - that represent two very different environments. On the graph, my Tide Clock is the GREEN line, which appears like a nice tidy sine wave. Above the zero line (+ve values) is the Third Quarter Error caused by the Sun and Moon being at 90 degrees to each other (the Neap Tide), when below the zero line (-ve values) it is the First Quarter error. As the Green line goes from +ve to -ve it is New Moon, from -ve to +ve it is Full Moon. The "jaggers' are due to the two high tides per day. On the Graph, positive values are when the "Official" Tide is ahead of the Tide Clock, negative values are when the "Official" Tide is lagging behind the Tide clock.

I don't use my Tide Clock as a NAVAID at all, just as a quick reference as to when to go swimming (or walking on the hard sand) at my local beach, where the approx 30 - 40 minute Tide clock error (at the Neaps) is of no consequence. I do wonder how many people have got into trouble using a Tide Clock - assuming it's correct. Certainly many of the very expensive (and beautiful Tide Clocks) have got that amazing air of "precision and quality" about them that I find enticing (yet evil ;-).

I have also attached the data I used to make the graph David.

Regards, Geoff Hitchcox, Christchurch, New Zealand.

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