On 19 August 2010 17:27, Malcolm Herring <malcolm.herr...@btinternet.com> wrote: > > The usual convention (Ordnance Survey for example) for land maps is to use > "Mean High Water". (Marine charts usually use "Mean High Water Springs" as > their dry land datum.)
There are exceptions. If a given area is covered in vegetation (eg salt marsh, or mangrove swamps) then it is usually put on the land side, even if it is technically below the high water mark. Otherwise you get situations where hundreds of meters of tangled plant growth are treated as sea, which just seems totally wrong. I've never seen a paper land map which listed a mangrove swamp as outside the coastline, though some of the PGS data does list them that way. (I don't know what marine maps do). Stephen _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
