next message in archive
next message in thread
previous message in archive
Index of Subjects
--Apple-Mail-592-679711554 Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit Hi Steve, On 19-Oct-09, at 11:31 PM, Stephen Shaw wrote: > There was even a story that the spatial > resolution is intrinsically much finer than is available to the > public, but > that the US military has deliberately detuned the public output so > it was less > precise, presumably so it could not be used for accurate nefarious > targetting > -- I'm guessing that this was an urban legend? Not at all. The US military used to intentionally add errors to its publicly available GPS signals via a protocol called SA (Selective Availability), adding time varying errors of up to 100 meters. SA was set to zero by an executive order of Bill Clinton on May 1, 2000. It is still a system capability of the GPS network and in theory could be turned on again if the US Department of Defens so-deemed. In practice, doing so now would create considerable havoc, and on September 17, 2007, the United States Department of Defense announced that future GPS III satellites will not be capable of implementing SA, eventually making the liquidation of SA permanent. Take a look at the SA section of the wikipedia article on GPS for further information, as well as the US Government document about the Clinton directive. http://en.wikipedia.org/wiki/GPS#Selective_availability http://usgovinfo.about.com/library/news/aa050300b.htm Cheers! Chris Christopher Majka Halifax, Nova Scotia, Canada B3H 2G5 c.majka@ns.sympatico.ca "If you don't know where you are going, you will wind up somewhere else." - Yogi Berra --Apple-Mail-592-679711554 Content-Type: text/html; charset=US-ASCII Content-Transfer-Encoding: quoted-printable <html><body style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; = -webkit-line-break: after-white-space; ">Hi Steve,<div><br><div><div>On = 19-Oct-09, at 11:31 PM, Stephen Shaw wrote:</div><br = class=3D"Apple-interchange-newline"><blockquote type=3D"cite"><div>There = was even a story that the spatial<br>resolution is intrinsically much = finer than is available to the public, but<br>that the US military has = deliberately detuned the public output so it was less<br>precise, = presumably so it could not be used for accurate nefarious = targetting<br>-- I'm guessing that this was an urban = legend?<br></div></blockquote></div><br></div><div>Not at all. The US = military used to intentionally add errors to its publicly available GPS = signals via a protocol called SA (Selective Availability), adding time = varying errors of up to 100 meters. SA was set to zero by an executive = order of Bill Clinton on May 1, 2000. It is still a system capability of = the GPS network and in theory could be turned on again if the = US Department of Defens so-deemed. In practice, doing so now = would create considerable havoc, and on September 17, 2007, = the United States Department of Defense announced that future = GPS III satellites will not be capable of implementing SA, eventually = making the liquidation of SA permanent. Take a look at the SA section of = the wikipedia article on GPS for further information, as well as the US = Government document about the Clinton = directive.</div><div><br></div><div><a = href=3D"http://en.wikipedia.org/wiki/GPS#Selective_availability">http://en= .wikipedia.org/wiki/GPS#Selective_availability</a></div><div><a = href=3D"http://usgovinfo.about.com/library/news/aa050300b.htm">http://usgo= vinfo.about.com/library/news/aa050300b.htm</a></div><div><br></div><div>Ch= eers!</div><div><br></div><div>Chris</div><br><br><div = apple-content-edited=3D"true"> <span class=3D"Apple-style-span" = style=3D"border-collapse: separate; color: rgb(0, 0, 0); font-family: = 'Times New Roman'; font-size: medium; font-style: normal; font-variant: = normal; font-weight: normal; letter-spacing: normal; line-height: = normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: = none; white-space: normal; widows: 2; word-spacing: 0px; = -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: = 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: = auto; -webkit-text-stroke-width: 0px; "><div style=3D"word-wrap: = break-word; -webkit-nbsp-mode: space; -webkit-line-break: = after-white-space; "><div><span class=3D"Apple-style-span" = style=3D"font-size: 14px; "><div>Christopher Majka</div><div>Halifax, = Nova Scotia, Canada B3H 2G5</div><div><a = href=3D"mailto:c.majka@ns.sympatico.ca">c.majka@ns.sympatico.ca</a></div><= div><br></div><div><i>"If you don't know where you are going, you will = wind up somewhere else."</i> - Yogi = Berra</div></span></div><div><br></div></div></span><br = class=3D"Apple-interchange-newline"> </div><br></body></html>= --Apple-Mail-592-679711554--
next message in archive
next message in thread
previous message in archive
Index of Subjects