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    Re: sextant without paper charts
    From: Peter Fogg
    Date: 2008 Nov 4, 11:14 +1100

    Lu writes:
    Look at a map of the Pacific Ocean.   It is dotted with thousands of islands, because the Pacific is a geologically and volcanically active region.   These islands grow thousands of feet from the ocean floor.   Stop a little early in your growth and you're an underwater mountain or seamount. 
    If we go back in time a very short period, geologically speaking, like 10,000-odd years, the oceans were about 180 metres lower than today.  The sea-level has fluctuated over time, with greater variations in the more distant past.  Whether by coincidence or not, some of the sea mounds off the east coast of Australia come to ... about 200 metres of the surface.
    Without data to support this assertion, I will nevertheless speculate that there are probably far more underwater mountains than above-the-water islands in the Pacific. 
    There are a few.

    Lu continues:
    Consider then the crudeness of our charting capabilities.   Satellites can't spot stuff below the water like they can above the water.   Side scan sonar is great -- if you've got the time and money to scan the ocean a few hundred yards at a swath.  Bottom line:  we really don't know what's out there in the great oceans.  
    Although this is changing, at least in our waters.  Australia claims a vast swathe of underwater territory (in the guise of 'economic interest') and has set about charting this realm in a systematic way.  All sorts of interesting  things are bobbing to the surface .. of our understanding.

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