[Talk-GB] VMD - coastline comparison map on ITO Map

Peter Miller peter.miller at itoworld.com
Sat Mar 17 21:57:45 GMT 2012

On 17 March 2012 10:22, Henry Gomersall <heng at cantab.net> wrote:

> On Sat, 2012-03-17 at 10:15 +0000, Peter Miller wrote:
> > I have just added a new coastline VMD comparison map to ITO Map which
> > focuses on high water, low water from VMD, coastline from OSM and also
> > tidal and non-tidal rivers.
> > http://www.itoworld.com/map/189
> Are all those red squiggles on the linked to page showing the high water
> mark actually static enough to map in the detail they have done? I've no
> idea about coastal features like that.

Good question.

In some places it is reasonably stable and probably worth mapping, and in
others, such as along the Suffolk coast by Felixstowe the shape often
changes significantly over only one winter.

It will certainly be worth making a quick check along many local coastlines
- For example, I have noticed that there is a point along the North Norfolk
coast where the OSM coastline abruptly changes from the high tide mark to
the low tide mark for no good reason:

I also note that the 'beach' tag is only recommended for use out as far as
high water (tagged with natural=coastline in OSM), but in places beaches
are shown out towards low water.

Should we may the surface (sand/mud/swamp/rocks etc) between high and low
tide? Possibly we should use natural=beach with 'tidal=yes'? Incidentally,
today I noticed that the OS 25K:1 maps show beaches, rocks etc out as far
as low water and only show sea beyond that point.


> Cheers,
> Henry
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