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Date: Tue, 15 Feb 2000 10:04:51 +0500
From: Tom Hanley <[log in to unmask]>
Subject: Sea Level
Sender: Tom Hanley <[log in to unmask]>


I should be able to answer this question for my colleague, but can't.

What is the definition of sealevel?  Topo maps say the datum is mean
sea level, but that may change from time to time.  Also, if the
Pacific and Atlantic are not at the same level, which is used as the
standard?  Does the "mean" take accont of both?  Or is there one
specific point that is taken as the standard zero?  Or do they use
760 mm Hg (on a clear day)?

What do the GPS satellites use as the standard zero?  Do they keep
sampling a specific ground-based station of defined elevation?  I
assume those would be redundant as the system was originally set up
by the military.

Thanks in advance and apologies for cross-postings.

Tom
-------------------------------------------------------------------
Tom Hanley, Department of Chemistry and Geology, Columbus State U.,
4225 University Ave., Columbus, Georgia 31907-5645.
Links to the ACRES project and to 1998 and 1999 pictures I took in Panama may be found at:
http://chemgeo.ColState.edu/th_hp.htm
VOX: 706-568-2074; FAX: 706-569-3133.
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