Image Name                   :  g96al
Boundaries                   :  Lat 49N to 72N ; Lon 172E to 234E
Color Scale, Upper (Red)     :  20 meters and higher
Color Scale, Lower (Magenta) : -20 meters and lower 
Data Max value               :  21.3 meters
Data Min value               : -21.5 meters
Illuminated from the         :  North 

  This is an image generated from 2'x4' geoid undulations covering the
state of Alaska and surrounding areas.  Some interesting features to 
note about this image are:

  The large (relatively) flat zone in the Northwest corner of the image 
represents the area of the former Soviet Union.  No gravity measurements from 
this area were available, so a synthetic gravity surface was used here.  
Tests have shown that the effect of this synthetic data on the Alaskan geoid
is minimal.

  The Aleutian trench, where the Pacific plate meets (and subducts under)
the North American plate, stands out as an elongated trench of highs (green to
red) and lows (blue to magenta).  Due to its extreme slopes, this image has
a somewhat "washed out" appearance around the Aleutian trench.  As such, 
a supplemental image was produced (g96al1) which focuses on the geoid in 
the Aleutian trench area.
  
  The Aleutian back-arc basin, appearing as a backward "C" curve 
extending off of the Aleutian trench in the Southwest corner of the image.
While not generating an island chain, this feature is large and geophysically
fascinating.

  The "bumps" seen in the Gulf of Alaska (south of the land mass) are
the effect of seamounts on the geoid.

  The high of reds in Southeast Alaska is a result of the Rocky Mountains
and Alaska Range on the geoid.

das/dgm 10/18/96