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.
TonyS
On 19/02/2019 08:01, Colin Smale wrote:
On 2019-02-19 04:03, Graeme Fitzpatrick wrote:
Not opposition, but for tidal areas, isn't this going to have the
same problems of whether you mark the "coastline" at the high- or
low-tide line?
Coastline is MHW, that is settled isn't it?
Water heights are more problematic though, because there are different
datums across the world. AFAIK there is no global default datum apart
from WGS84 geoid height which no mariners ever use directly. All water
levels/heights therefore need to be related to a datum.
Depth however is local and is just the difference in height between
the water level and the bottom. Can you even have a negative depth?
Floating above the water?
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