Stupid Attorney taling about GPS's

Tarver Engineering wrote:

"Peter" wrote in message
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Tarver Engineering wrote:


"Peter" wrote in message
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Ron Lee wrote:


"Dave" wrote:




Unaugmented GPS is accurate to within 7.2 meters longitudinally.


Go say that in sci.geo.satellite-nav and see what happens.



Probably not a bad number.

Only if the usual caveats are added; i.e. 95% of the time and assuming

the

receiver has good reception conditions. Any attorney trying to

discredit

GPS evidence will naturally focus on the 5% of the time when the

position

could be off by more than the nominal accuracy and on obstructions,
multi-path reflections, RFI, etc. that can degrade performance,
particularly in a covert installation where the antenna is unlikely to

be

optimally placed for good reception.


False.

The convergence of the GPS Jacobian does not occur for the conditions

you

describe. One of the major advantages of GPS over current ground based
navigation is the difficulty of spoofing the system.


I suggest you read your "GPS World" issues some more. Improvement of
integrity monitoring was one of the main reasons for requiring

augmentation

of GPS.


False.

The failure to monitor the integrity of the WAAS signal is why the test bit
remained set until recently. The integrity issues were WAAS integrity
issues with no relevence to GPS.

Unaugmented GPS has insufficient integrity monitoring.
http://www.cts.cv.ic.ac.uk/html/Rese...p?seminarID=62
:
"The assessment results also indicated that the current GPS system cannot
meet the RNP in most of the cases and the current integrity monitoring
mechanism is inadequate for providing the necessary integrity monitoring
capability. Therefore, this study suggests that augmentation systems are
needed to support the navigation function for all phases of flight." Jan.
28, 2004, Imperial College, London, Dr. Shaojun.


Evidence already presented in this court case also indicates
some of the problems cited above which resulted in momentary errors of
miles rather than meters.


A maomentary error with what equipment?

Apparent position errors recorded by the monitoring equipment used in the
investigation being discussed.


I'm an advocate of GPS navigation but it is not infallible and carries no
absolute 7 m accuracy guarantee.


So far you are zero for two.

The "Standard Positioning Service Performance Standard," Table 3.6
http://www.navcen.uscg.gov/gps/genin...ndardFINAL.pdf
gives the post-SA specification for horizontal position as being within 13m
95% of the time assuming the receiver can see all signals from satellites
above the horizon. The vertical spec. is 22m, 95% of the time. Actual
performance has exceeded these specifications but AFAIK the specification
has not been updated.
Feel free to cite any GPS specification that guarantees 7 m accuracy 100%
of the time regardless of reception conditions.