<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">On 12/8/2012 4:26 PM, Andrew Rich
wrote:<br>
</div>
<blockquote cite="mid:B076854C17DC440B9E9206A2A53117A6@MacBook"
type="cite">
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
<meta name="GENERATOR" content="MSHTML 8.00.6001.19298">
<style></style>
<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. <br>
<br>
<br>
<br>
</body>
</html>