Subject: Re: Dutch provincial North sea<br/>
Date: Dec 17, 2001 @ 15:38<br/>
Author: granthutchison (&quot;granthutchison&quot; &lt;granthutchison@...&gt;)<br/>
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<div id="ygrps-yiv-143142883">Peter:<br/>
<blockquote><span title="ireply"> &gt;`laag laagwaterlijn spring&#39; <br/>
&gt; [what is meant here I don&#39;t know, it is a low tide watermark, but <br/>
&gt; presumably a specific one - the quotes are not added by me]<br/>
<br/>
 </span></blockquote>Low low water is the lower of the two daily tides (most places, most<br/>
of the time, the two tides differ in height). Low low water spring is<br/>
the same measure applied to the spring tide - the lowest/highest tide<br/>
of the (lunar) month. The measurement is usually meaned over a period<br/>
of years.<br/>
As a datum, it seems to be favoured in Belgium and the Netherlands,<br/>
for some reason.<br/>
<br/>
It&#39;s a pretty low tide, but not the absolute lowest you can get -<br/>
spring tides are lower in January (when the Earth is closest to the<br/>
sun); when the moon is at its closest to the Earth; and during an<br/>
eclipse (when the gravitational pull of moon and sun are perfectly<br/>
aligned). Put all those factors together on the same day and you get a<br/>
&quot;king perigean eclipse tide&quot;. Mark your diary for the next one - 18<br/>
January 3089.<br/>
<br/>
Grant</div>