Subject:
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Re: GPS
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 4 Jan 2001 23:20:38 GMT
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Original-From:
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Martin <martin@mediax[ihatespam].com>
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Reply-To:
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martin@mediax/spamless/.com
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Viewed:
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679 times
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Eggers Tom W Civ USAFA/DFCS wrote:
> Sometime a little over a year ago, the United States Government
> turned off the "feature" of GPS that reduced the accuracy to 30
> meters. So you now get the full military accuracy of the system,
> something like 3 meters (10 feet), still a bit too large for
> navigating around a room.
First: That is not full military accuracy. As per
http://www.navcen.uscg.mil/faq/gpsfaq.htm
GPS provides two levels of service -- a Standard Positioning Service
(SPS) for general public use and an encoded Precise Positioning Service
(PPS) primarily intended for use by the Department of Defense. SPS
signal accuracy is intentionally degraded to protect U.S. national
security interests. This process, called Selective Availability (SA),
controls the availability of the system's full capabilities. The SPS
accuracy specifications, given below, include the effects of SA.
http://users.erols.com/dlwilson/gps.htm
This is a page which talks all about GPS accuracy.
There are military GPSes which can actually get down to 5cm accuracy if
you let them sit still for about 30 seconds. Civilian units typically
get no better than three meters when SA is turned off, as it is now.
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