<div dir="ltr"><div class="gmail_default" style="font-family:georgia,serif;font-size:small">Submarine? Maybe you should just fix that leak? :)<br></div></div><div class="gmail_extra"><br clear="all"><div>Pete Hardie<br>--------<br>
Better Living Through Bitmaps</div>
<br><br><div class="gmail_quote">On Tue, Feb 26, 2013 at 7:28 AM, Jim Lynch <span dir="ltr"><<a href="mailto:ale_nospam@fayettedigital.com" target="_blank">ale_nospam@fayettedigital.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">On 02/25/2013 11:59 PM, Sean Kilpatrick wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
The civilian rade GPS units by and large only claim to be accurate within 50 feet or so -- in any direction. That certainly was proven true during a recent trip to Amelia Island, Florida -- just north of Jacksonville.<br>
<br>
the unit reported elevation on different days between -50 and +75 feet, when the car was parked ~maybe~ eight feet above mean high tide.<br>
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</blockquote></div>
I agree, my sailboat varies from being a submarine to a low flying aircraft when I'm on the water according to the gps. Also the mathematical model of the earth GPSes us doesn't not accurately describe the actual surface of the earth.<br>
<br>
There are a number of surface models, including sphere oblate spheroid, ellipsoid, geoid and others. Each has it's accuracies and inaccuracies. To compound matters, the actual surface of the earth constantly changes its shape.<br>
<br>
<br>
It's best for hiking to use the altimeter as a relative measuring device. "I am ascending" or "I am descending" or "This hill is 50 feet higher than my house".<br>
<br>
Jim.<span class="HOEnZb"><font color="#888888"><br>
Jim.</font></span><div class="HOEnZb"><div class="h5"><br>
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