The North American Vertical Datum of 1988: the reference surface most South Florida cities use when they set a seawall height. When a code says 5 ft NAVD88, it means five feet above that datum, not five feet above the water you can see. NOAA's National Geodetic Survey describes NAVD88 as still the official vertical datum of the National Spatial Reference System, and plans to replace it with a new gravity-based datum; heights will change when that happens, so always note which datum a survey uses. NAVD88 is not mean sea level and it is not mean low water, so a height stated in one is a different number in the other. A licensed surveyor can give you your cap elevation in NAVD88.
Source: NOAA National Geodetic Survey, New Datums: Replacing NAVD 88 and NAD 83 · NOAA CO-OPS, Datum definitions · Checked 2026-10
Which agencies are involved, what each one wants, and the order they want it in.
One email. Unsubscribe in a click.
Done — it is on the way to your inbox. Not there in a minute? Check your Promotions or Spam folder, and move it to your inbox so the next ones arrive.