[pct-l] RE: GPS Altimiters

[msarahm at cox.net (Sarah)]

I've recently been crunching some longitude-latitude-altitude numbers for my job, and I was told that most GPS units report elevation according to the WGS84 standard.  The elevation isn't truly above sea level, but above an approximate spheroid that describes the earth's shape.  The spheroid, or geoid (I forget the terminology), is close to sea level, but no cigar.  I have also been told that GPS is not nearly as accurage in elevation as it is in lon-lat as another person has already written.

Sarah
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Date: Sat, 17 Sep 2005 21:43:20 -0700
From: Tortoise <Tortoise73@charter.net>
Subject: Re: [pct-l] GPS Altimeters

I asked the question about the accuracy of GPS vs. barometer-type 
altimeters. I know my old low-price consumer GPS sometimes have 
problems. I've been standing on a beach and the GPS tells me I'm ~200 
feet below sea level. I haven't played enough with my GPS to see how 
accurate it will stay once I set the approximate altitude once. Are 
newer units more accurate, or are the units bumping at the limits of the 
technology and method?

Tortoise