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<p>Quite right. For OSM purposes I suggest depth in metres, if water
is tidal=yes also tidal_range in metres. <br>
</p>
<p>I can't think of any reason to try to replicate nautical charts
and tide tables. And when planning navigation I do not consider
not using formal navigation charts and tables specific to that
purpose.<br>
</p>
<p>TonyS</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 19/02/2019 10:56, Colin Smale wrote:<br>
</div>
<blockquote type="cite"
cite="mid:64dd3826dff1c934c5acf87c0ef0a2e5@xs4all.nl">
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<p>On 2019-02-19 11:11, Tony Shield wrote:</p>
<blockquote type="cite" style="padding: 0 0.4em; border-left:
#1010ff 2px solid; margin: 0">
<p>Depth of water in tidal areas can vary enormously. People
using depth for navigation and general use would expect to use
depth at MLWS (Mean Low Water Springs) and add increments
based on tide tables, I suggest that OSM does the same. Use
the tidal tag and perhaps a tidal-range tag, in metres,
tidal_range is the difference between MHWS (Mean High Water
Springs) and MLWS.</p>
<p>note - Spring tides are the highest and lowest forecast tides
and are based on the relative position of the earth, moon and
sun.</p>
</blockquote>
<p>Indeed, they are astronomical predictions, but not forecasts.
They are not in themselves good enough for planning a (route to
a) berth in a harbour for example. There are many other factors
influencing the actual water level, like global/local weather
conditions and seiche waves. Depth is of course also affected
by dredging operations...</p>
<p>Should OSM aim to replicate the Admiralty Charts and tide
tables?</p>
<p><br>
</p>
<br>
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