Quite right. For OSM purposes I suggest depth in metres, if water is
tidal=yes also tidal_range in metres.
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.
TonyS
On 19/02/2019 10:56, Colin Smale wrote:
On 2019-02-19 11:11, Tony Shield wrote:
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.
note - Spring tides are the highest and lowest forecast tides and are
based on the relative position of the earth, moon and sun.
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...
Should OSM aim to replicate the Admiralty Charts and tide tables?
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