[NatureNS] GPS deal - spatial resolution

From: Hubcove@aol.com
Date: Tue, 20 Oct 2009 09:08:44 EDT
To: naturens@chebucto.ns.ca
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As Chris said, the degrading of the GPS position was very much  a US 
policy, apparently  primarily to degrade targeting information. The  way major 
manufacturers got around the problem was by marketing Differential  GPS. 
Receivers in significant navigation locations, Chebucto Head for example,  
received the GPS signal, compared it to the actual position of the receiver and  
transmitted the correction to shipborne receivers on a frequency of  around
300khz. Prior to that, while the absolute accuracy of GPS was  superior to 
Loran, the relative accuracy with Loran was very high. In other  words, if 
you put something in the water and noted the Loran reading, it would  still 
be very close to the same reading when you came back, assuming of course  it 
was anchored. Loran errors can be quite large, but are generally  constant.
 
Peter Stow
(ancient sea captain} 
Hubbards

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<DIV><FONT size=3D3>As Chris said, the degrading of the GPS position was=
 very much=20
a US policy, apparently &nbsp;primarily to degrade targeting information.=
 The=20
way major manufacturers got around the problem was by marketing Differenti=
al=20
GPS. Receivers in significant navigation locations, Chebucto Head for exam=
ple,=20
received the GPS signal, compared it to the actual position of the receive=
r and=20
transmitted the correction to shipborne receivers on a frequency of=20
around</FONT></DIV>
<DIV><FONT size=3D3>300khz. Prior to that, while the absolute accuracy of=
 GPS was=20
superior to Loran, the relative accuracy&nbsp;with Loran was very high. In=
 other=20
words, if you put something in the water and noted the Loran reading, it=
 would=20
still be very close to the same reading when you came back, assuming of co=
urse=20
it was anchored. Loran errors can be quite large, but are generally=20
constant.</FONT></DIV>
<DIV><FONT size=3D3></FONT>&nbsp;</DIV>
<DIV><FONT size=3D3>Peter Stow</FONT></DIV>
<DIV><FONT size=3D3>(ancient sea captain}</FONT>&nbsp;</DIV>
<DIV><FONT size=3D3>Hubbards</FONT></DIV></FONT></BODY></HTML>

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