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Ngvd 29 Vs Navd 88

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Found this and though it might be of interest to some.

 

NGVD 29 is a fixed datum adopted as a national standard geodetic reference for

heights but is now considered superseded.  NGVD 29 is sometimes referred to as

Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological

Survey Topographic Quads.  NGVD 29 was originally derived from a general

adjustment of the first-order leveling networks of the U.S. and Canada after

holding mean sea level observed at 26 long term tide stations as fixed.

Numerous local and wide-spread adjustments have been made since establishment in

1929.  Bench mark elevations relative to NGVD 29 are available from the National

Geodetic Survey (NGS) data base via the World Wide Web at

National Geodetic Survey.

 

NAVD 88 is a fixed datum derived from a simultaneous, least squares, minimum

constraint adjustment of Canadian/Mexican/United States leveling observations.

Local mean sea level observed at Father Point/Rimouski, Canada was held fixed as

the single initial constraint.  NAVD 88 replaces NGVD 29 as the national

standard geodetic reference for heights.  Bench mark elevations relative to

NAVD 88 are available from NGS through the World Wide Web at

National Geodetic Survey.

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