Re: GPS and altitude (was speedo error) diminishing Alfa content.

[ALfactor@domain.elided]

In a message dated 1/26/02 10:47:03 PM Central Standard Time, 
schaferbs@domain.elided writes:

<< There is no adjustment for altitude on any GPS.  GPS is dependent on RF 
 signals from satelites (at least 3 to give correct location, speed  and 
 altitude) so altitude of the receiver has no bearing on position, speed or 
 altitude. >>

Actually my receiver has a way to manually enter altitude. According to the 
manual 3 satellites will give a position fix and as well as speed and 
heading.  4 satellites are required to compute elevation.  Magellan calls 
these two modes 2D (manually entered) and 3D (GPS computed).  I don't know 
why there is a feature for manually entered altitude unless altitude induces 
an error similar to the height of eye correction for celestial navigation.  
If so I would imagine it would be more noticeable in aeronautical navigation. 
 Maybe I'll experiment with taking fixes with different altitudes entered and 
see if the EP changes.  Actually I was thinking of getting out my sextant and 
taking a fix to see how close I could come. (way too much time on my hands)

Either way my speedo is still reading too slow.

Mitch Fisher
'74 Spider
37-42.9N
121-55.3W
353' above sea level

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