� Local Mean Sea Level (LMSL) › determined at individual tide gages � Sea Level Datum (SLD) of 1929 › constrained at 26 tide gages in the U.S. and Canada � National Geodetic Vertical Datum of 1929 (NGVD 29) › renamed from SLD of 1929 to avoid confusion with LMSL � North American Vertical Datum of 1988 (NAVD 88) › constrained only at Pointe au Pere gage on St. Lawrence River