GEOID06 is a refined hybrid geoid mode for Alaska only.
GEOID06 converts between the U.S. ellipsoidal datum, NAD 83, and the U.S. vertical datum, NAVD 88. GEOID06 is built largely on the USGG2003 gravimetric geoid.
It uses limited GPS derived ellipsoid heights on leveled bench marks in both the U.S. and Canada to map the systematic differences between the gravimetric geoid surface and NAVD 88. The resulting model is suitable for use in converting NAD 83 ellipsoid heights into equivalent NAVD 88 orthometric heights.
This model is superseded by GEOID09.
