[Tagging] Tidal inlets / creeks

charlie at cferrero.net charlie at cferrero.net
Wed Jan 19 06:50:55 GMT 2011

Stephen Hope (slhope at gmail.com) wrote:

> I don't agree.  This is a good general rule, but the general
> convention on most maps is that the coast goes on the SEA side of
> things like coastal swamps and mangroves.  As a rule of thumb, if it
> has plants growing though the water, it's land, not sea, even if it
> happens to be wet.
> Doing this your way looks OK at higher zoom levels, but as the
> coastline way is used to make the country shapes for low zoom levels,
> these ways are out of place. In most temperate areas, the difference
> is so small you can't really tell, but this can be very important in
> tropical areas where the mangroves can be many km wide.  In these
> cases, I've never seen a map that shows the coast on the inner edge,
> and trying to do so is just wrong.
> Stephen

So is there any consensus on where the coastline goes when you have  
major areas of saltmarsh and/or mangrove?  At the moment in OSM the  
Abu Dhabi coastline follows dry land (i.e. above mean high water) and  
there are huge expanses of mangroves and saltmarshes sitting in the  
sea, e.g.:

Google, however, has put the coastline around the outside of the  
marshes and the result looks nothing like a good representation of  
what's actually there:
http://maps.google.co.uk/maps?q=abu+dhabi&safe=on&ie=UTF8&hq=&hnear=Abu+Dhabi+-+United+Arab+Emirates&ll=24.521513,54.507294&spn=0.08215,0.241699&z=13  In fact, you can see island labels floating in the middle of apparently dry  

The trouble with putting the coastline around the outside of the  
saltmarshes / mangroves is that it is very difficult to figure out  
where this boundary is from aerial photography.

Dry land is usually easy to see.  Obviously it would be better to  
survey it in person, but given the shallowness of the water that would  
be impossible unless you used a hovercraft or kayak.


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