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HEIGHT SYSTEMS

DATUMS
North American Vertical Datum of 1988 (NAVD 88)
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›Defined by one height (Father Point/Rimouski)
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›Water-level transfers used to connect leveling across the Great Lakes
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›Geopotential Numbers
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›Helmert orthometric heights
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›Hhel - C/Ga;  Ga = Mean value of gravity along the plumb line
                  between the geoid and surface, estimated using
                  Helmert’s reduction, I.e., g + 0.0424xHo.
           g = gravity at the surface in gals
         Ho = approximate height in kilometers
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