21
HEIGHT
SYSTEMS
DATUMS
DATUMS
National Geodetic
Vertical Datum of 1929 (NGVD 29)
›Defined by heights of
26 tidal stations in the U.S. and Canada
›Tide gages were
connected to the vertical network by leveling from tide gage staffs to bench marks
›Water - Level
transfers used to connect leveling across the Great Lakes
›Normal orthometric
heights
H - C/Ga; Ga - Normal
gravity based on formula
