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<DIV><FONT size=2 face=Arial>Thanks - will go find a hill </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>- Andrew - </FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=wa8lmf2@aol.com href="mailto:wa8lmf2@aol.com">Stephen H. Smith</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=vk4tec@tech-software.net
href="mailto:vk4tec@tech-software.net">Andrew Rich</A> ; <A
title=aprssig@tapr.org href="mailto:aprssig@tapr.org">TAPR APRS Mailing
List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, December 09, 2012 7:36
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [aprssig] GPS question</DIV>
<DIV><BR></DIV>
<DIV class=moz-cite-prefix>On 12/8/2012 4:26 PM, Andrew Rich wrote:<BR></DIV>
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<DIV><FONT size=2 face=Arial>I am not sure I have asked this before but I
will ask it again.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2 face=Arial>I have a GPS on the side of a building and it
can only see half the sky - to the north</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2 face=Arial>What is curious - is that when plotted on
google earth - the postion is north of where it should be </FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2 face=Arial>I will move it into full view of the sky and
see what that does </FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2 face=Arial>- Andrew - </FONT></DIV><BR></BLOCKQUOTE><BR>A
gps receiver should be able to function normally WITHOUT seeing the entire
sky; they do this all the time on car dashboards. <BR><BR>Most likely
you either have the unit set for a datum other than WGS84 (the GLOBAL grid
system created by and for GPS). <BR><BR>Or the device is being confused
by reflections from nearby structures. Since GPS works by timing the
difference in time of arrival of signals from multiple satellites, multipath
reflections that add to path length (and thereby delay the time of arrival of
signals) will translate directly into a shifted position. In downtown
large-city "urban canyons" of glass-faced high-rise buildings that bounce the
1575 MHz GPS signals every which way, it's not uncommon to see GPS "go nuts"
and jump back and forth several blocks.
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