shrug-l: RE: Elevation Unit Reference for NAVD88

Sykes, John John.Sykes at
Tue Jul 10 09:25:19 EDT 2012


NAVD88 is a datum.  Elevations in NAVD88 relate to the NAD83 ellipsoid and has little relationship to local sea level.  Therefore, "xx.xx ft (NAVD88)" would be the proper citation.

I believe that elevations relating to local sea level would be listed as "xx.xx ft( AMSL)"  which would refer to a local benchmark that has been surveyed to the local sea level.  NOAA costal charts list the various sea level datums for a specific location, and the survey data is referenced to it.  I might be wrong on the second point, it has been several years since I had to work with sea level data.

Again, someone feel free to jump in on this, it has been a long time since I worked with sea level data (1999 in the Florida Keys).

-- John

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From: shrug-l-bounces at [mailto:shrug-l-bounces at] On Behalf Of Thomas, Jim
Sent: Tuesday, July 10, 2012 8:50 AM
To: shrug-l at
Subject: shrug-l: Elevation Unit Reference for NAVD88

I all,

I have a survey question related to elevation units.  Since NAVD88 ZERO and MSL Zero are not necessarily the same, is it wrong to express elevation units that reference NAVD88 as 'FT AMSL'?  Or is 'ft' more appropriate?

I've seen data stored this way and I would like to suggest the appropriate unit.


Jim Thomas, GISP | GIS Analyst | Golder Associates Inc.
9428 Baymeadows Road, Suite 400, Jacksonville, Florida, USA 32256
T: +1 (904) 363-3430 | F: +1 (904) 363-3445 | E: jim_thomas at<mailto:jim_thomas at> |<>

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