[Tagging] Tidal inlets / creeks

Stephen Hope slhope at gmail.com
Wed Jan 19 07:33:50 GMT 2011

On 19 January 2011 16:50,  <charlie at cferrero.net> wrote:
> 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
> land.

That's more because Google has not mapped the area properly, than to
do with their mapping method..  They've just run a border around a
whole area of little islands and marshes, ignoring some pretty obvious
clear water channels.

> 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.

I usually find the opposite. The outside edge of mangroves is quite
clear, mapping the dry line is harder, as it twists and turns a lot.
Here's an example, Hunter and Glennie inlets in northern Queensland,


If you compare the map and satellite views, You'll see that the
coastal line follows the outer edge of the mangroves.  But if you look
at PGS hightide data (not visible here), the majority of that whole
dark green area is tidal. It's got little pockets of dry land in the
middle of the swamps, but not much.  The google coastal line, while
quite rough, is a much better representation of the real coast than
the dry land border would be.


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