On 2008-04-07, clifto <clifto@gmail.com> wrote:
> Richard B. Gilbert wrote:
>> clifto wrote:
>>> News wrote:
>>>>clifto wrote:
>>>>>Kurt wrote:
>>>>>>"Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
>>>>>>
>>>>>>>GPS, or at least the civilian version of it, is only accurate to within
>>>>>>>about 300 feet or 100 meters.
>>>>>>
>>>>>>It's been changed for a few years, now more like 15 meters. Clinton was
>>>>>>the one that changed that.
>>>>>
>>>>>http://www.navcen.uscg.gov/faq/gpsfaq.htm#Standard
>>>>>
>>>>>SPS provides accuracy's of (for position, the accuracy with respect to
>>>>>geographic, or geodetic coordinates of the Earth) within:
>>>>>100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300 meters
>>>>>(99.99% prob.) horizontal 340 nanoseconds time (95% prob.)
>>>>
>>>>"What is the status of Selective Availability (SA)?
>>>
>>> What does SA have to do with the 2008 accuracy specification I posted?
>>
>> IIRC, SA encrypted the low order bits in order to prevent GPS being used
>> for weapons targeting and other anti-social behavior.
>
> That's true, but Clinton shut it off in 2001 and it hasn't been a problem
> for nearly seven years now.

Sure, but no one in the government said they wouldn't turn it back on if
they felt like it which is why their SPS accuracy claims still always
include the effects of SA.

In fact the paragraph just above the accuracy specifications you quoted
says, in part,

"The SPS accuracy specifications, given below, include the effects of SA."

which, I guess, is what SA has to do with the 2008 accuracy specification
you posted.

Dennis Ferguson