Re: [Paddlewise] GPS errors

From: <HTERVORT_at_aol.com>
Date: Tue, 16 Mar 1999 00:16:07 EST
Great input everyone.  Especially Dan and ?WILAX? (who is that masked poster
who posts knowledgeably and drives too fast?).

I have little more input to help with this conundrum, but I'll try to at least
guess.

<Multipath usually shows up as a jump.  Question, were you docked when you did
these tests?>
No, the ones involved (a friend and others in a class) were actively sailing
about, practicing navigational and sailing skills.

<Was there a lot of stuff around like buildings, bridges etc?>
I assume no closer than 1/2 to 1 nM.  But even if, they would be moving away
and toward.

<The antenna system had failed and the unit was dead reckoning.>
Wouldn't the officer on watch (or previous watch) have needed to manually
initialize the unit to start DR?  I never heard of a GPS doing DR, so I assume
you are referring to some fancy nav system which integrates a GPS receiver for
obtaining fixes?
 
<Are you SURE this unit was actually LOCKED onto the constellation?>
Nope.

<Finally, how was altitude being determined?  Was it entered manually and you
were navigating in 2D mode or were you resolving lat/long and altitude?>
Huh?  Sorry, I'm the dummy who asked the question.  Actually, the handhelds
were confirmed (supposedly) as being accurate.  Since the console unit was
mounted in a sailboat rather than an RV or helicopter, I would be surprised if
anyone ever dinked with the altitude setting after initial installation.  Of
course, its precisely because it should always be set for sea level + antenna
height that nobody would ever think to check it, and since no instrument is
idiot proof. . .   

<Finally, finally, some units have an oscillator offset check in the service
screen.  There is a tolerance for offset on some units....maybe this unit is
.....broken.>
Could be, but your analytical skills are functioning.  Thanks

Harold
So. Cal., so impressed - thanks guys.

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Received on Mon Mar 15 1999 - 21:17:14 PST

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