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Cellular forums Home > Archive > Garmin GPS > February 2008 > GPS Accuracy
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| Rupert Brooke 2008-02-14, 10:33 am |
| GPS are good, but still under restrictions...some interesting details.
GPS Positioning Services Specified In The Federal Radionavigation Plan
Precise Positioning Service (PPS)
a.. Authorized users with cryptographic equipment and keys and specially
equipped receivers use the Precise Positioning System. U. S. and Allied
military, certain U. S. Government agencies, and selected civil users
specifically approved by the U. S. Government, can use the PPS.
b.. PPS Predictable Accuracy
a.. 22 meter Horizontal accuracy
b.. 27.7 meter vertical accuracy
c.. 200 nanosecond time (UTC) accuracy
--------------------------------------------------------------------------------
Standard Positioning Service (SPS)
a.. Civil users worldwide use the SPS without charge or restrictions. Most
receivers are capable of receiving and using the SPS signal. The SPS
accuracy is intentionally degraded by the DOD by the use of Selective
Availability.
b.. SPS Predictable Accuracy
a.. 100 meter horizontal accuracy
b.. 156 meter vertical accuracy
c.. 340 nanoseconds time accuracy
c.. These GPS accuracy figures are from the 1999 Federal Radionavigation
Plan. The figures are 95% accuracies, and express the value of two standard
deviations of radial error from the actual antenna position to an ensemble
of position estimates made under specified satellite elevation angle (five
degrees) and PDOP (less than six) conditions.
d.. For horizontal accuracy figures 95% is the equivalent of 2drms
(two-distance root-mean-squared), or twice the radial error standard
deviation. For vertical and time errors 95% is the value of two-standard
deviations of vertical error or time error.
e.. Receiver manufacturers may use other accuracy measures.
Root-mean-square (RMS) error is the value of one standard deviation (68%) of
the error in one, two or three dimensions. Circular Error Probable (CEP) is
the value of the radius of a circle, centered at the actual position that
contains 50% of the position estimates. Spherical Error Probable (SEP) is
the spherical equivalent of CEP, that is the radius of a sphere, centered at
the actual position, that contains 50% of the three dimension position
estimates. As opposed to 2drms, drms, or RMS figures, CEP and SEP are not
affected by large blunder errors making them an overly optimistic accuracy
measure
f.. Some receiver specification sheets list horizontal accuracy in RMS or
CEP and without Selective Availability, making those receivers appear more
accurate than those specified by more responsible vendors using more
conservative error measures.
Source: http://www.colorado.edu/geography/g...es/gps/gps.html
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| James Robinson 2008-02-14, 12:33 pm |
| "Rupert Brooke" <yl617@yahoo.com> wrote:
> GPS are good, but still under restrictions...some interesting details.
>
> GPS Positioning Services Specified In The Federal Radionavigation Plan
> Precise Positioning Service (PPS)
> a.. Authorized users with cryptographic equipment and keys and
> specially
> equipped receivers use the Precise Positioning System. U. S. and
> Allied military, certain U. S. Government agencies, and selected civil
> users specifically approved by the U. S. Government, can use the PPS.
> b.. PPS Predictable Accuracy
> a.. 22 meter Horizontal accuracy
> b.. 27.7 meter vertical accuracy
> c.. 200 nanosecond time (UTC) accuracy
>
> -----------------------------------------------------------------------
> ---------
>
> Standard Positioning Service (SPS)
The Selective Availability system (SA) has been disabled since May 2000.
Everybody now had access to PPS.
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| ben brugman 2008-02-14, 3:33 pm |
|
>
> The Selective Availability system (SA) has been disabled since May 2000.
> Everybody now had access to PPS.
The error has been set to Zero for the SA system. But the militairy system
is still different from the civilian system. The militairy system is still
heavely encripted and can not be used by civilians. So the civilian system
is accurate, the militairy system still has some advantages in precision.
ben
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| Simon Slavin 2008-02-16, 10:33 pm |
| On 14/02/2008, Rupert Brooke wrote in message <ZOZsj.540$dh.385@trnddc01>:
> GPS are good, but still under restrictions...some interesting details.
Why did you bother posting this ? Paragraph 1 has wrong numbers in. 2 a
and b are out of date. c and d are obsolete (more satellites with better
radio equipment). e and f have no information (nobody believes
manufacturer's figures).
Simon.
--
http://www.hearsay.demon.co.uk
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| Rupert Brooke 2008-02-17, 3:33 pm |
| Please note the source data with the posting...If Colorado.edu is wrong, by
all means show them there their numbers are wrong and tell them to update.
The rather rudimentary postings regarding GPS Accuracy previously had very
unscientific methods of verifying accuracy, or quoted manufacturers claims.
(Colo.edu cited the various mfg claims, and noted their skepticism. They
did not say they were right.) At least Colo.edu has some science and
research behind it, not mfg or user opinion. Subsequent postings have had a
more scientific and more current info. Subscribers have started looking for
more accurate answers. That is a good thing.
All net postings should have dates so people know whether to look for newer
reports & corroborations. For the aspect that some changes have occurred
since their (Colo.edu) hypothesis, I do apologize. Rupert
"Simon Slavin" <slavins.delete.these.four.words@hearsay.demon.co.uk> wrote
in message news:fp80qb$7v6$2$83
00dec7@news.demon.co.uk...
> On 14/02/2008, Rupert Brooke wrote in message <ZOZsj.540$dh.385@trnddc01>:
>
>
> Why did you bother posting this ? Paragraph 1 has wrong numbers in. 2 a
> and b are out of date. c and d are obsolete (more satellites with better
> radio equipment). e and f have no information (nobody believes
> manufacturer's figures).
>
> Simon.
> --
> http://www.hearsay.demon.co.uk
| |
|
| In article <M31uj.3736$0%3.1181@trnddc06>,
"Rupert Brooke" <yl617@yahoo.com> wrote:
> All net postings should have dates so people know whether to look for newer
> reports & corroborations. For the aspect that some changes have occurred
> since their (Colo.edu) hypothesis, I do apologize. Rupert
ALL Net Postings DO have Dates and Times embedded in them ALREADY,
YOU just don't understand the technology your using........
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| Bad Idea 2008-02-17, 10:33 pm |
| On Feb 17, 1:47=A0pm, "Rupert Brooke" <yl...@yahoo.com> wrote:
>
> All net postings should have dates so people know whether to look for newe=
r
> reports & corroborations. =A0For the aspect that some changes have occurre=
d
> since their (Colo.edu) hypothesis, I do apologize. Rupert
>
Right. Of course, on the page you sourced, near the top you saw:
"Revised: 05/01/2000". That's almost eight years ago.
The next sentence says:
"NEW! Selective Availability Turned Off as of May 2, 2000!"
Hope this helps.
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"You" <you@shadow.orgs> wrote in message news:you-6136E3. 12491117022008@netne
ws.worldnet.att.net...
> In article <M31uj.3736$0%3.1181@trnddc06>,
> "Rupert Brooke" <yl617@yahoo.com> wrote:
>
> ....YOU just don't understand the technology your using........
you're
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