USGG2012 is a refined gravimetric model of the geoid
in the United States and other territories,
which supersedes the previous models
USGG2009 and
USGG2003.
For USGG2012 in CONUS regions, heights range
from a low of -52.53 meters (magenta) in the Atlantic Ocean
to a high of 3.47 meters (red) in the Labrador Strait.
USGG2012 refers to a GRS 80 ellipsoid,
centered in the IGS08 (2005.00) reference frame, and is the
best geopotential surface that approximates Mean Sea Level (MSL).
USGG2012 is NOT for converting between NAD83 and NAVD88.
USGG2012 is suitable for use with WGS84 and scientific applications.