IR & Water, a higher perspective

[Joshua_Putnam <josh@xxxxxxxxxxxx>]

The discussion of IR and water reminded me of an
interesting set of satellite photos I have of a local
gravel pit on the shore of Pugest Sound.

One is visual-spectrum black-and-white.  The shoreline is
clearly visible, as are the wakes of boats moving on the
Sound, and in some areas the texture of the water.

The other is B&W infrared, and the view is much different:
the Sound appears darker in general, but much more
transparent as well -- you can, for example, clearly see
sunken ships under 30-40 feet of water, and the outline of
underwater features along the shoreline.

This makes me think that much of this debate has been
people talking past each other, since there are two very
different questions really being asked: how well does
infrared reflect from the surface of the water, and how
quickly does the water absorb infrared that does penetrate
the surface?  From looking at the satellite photos, I would
say that IR is less prone to reflect back from the water
surface, leaving deep water looking black, but that IR does
penetrate water reasonably well, since solar IR can reflect
back from significant depths well enough to show the sunken
ships.

-- 

 Josh@xxxxxxxxxxxx  is  Joshua Putnam / P.O. Box 13220 / Burton, WA 98013
                       "My other bike is a car."                   
                     http://www.wolfenet.com/~josh/
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