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sci.geo.satellite-nav (Global Satellite Navigation) (sci.geo.satellite-nav) Discussion of global navigation satellite systems (GNSS). Topics include the technical aspects of GNSS operation, user experiences in the use of GNSS, information regarding GNSS products and discussion of GNSS policy (such as GPS selective availability).

DoT Disses DoD’s GPS Chops



 
 
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  #1  
Old January 14th 14, 08:11 PM posted to sci.geo.satellite-nav
Sam Wormley[_2_]
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Default DoT Disses DoD’s GPS Chops

Thanks Jon

DoT Disses DoD’s GPS Chops
http://gpsworld.com/dot-disses-dods-gps-chops/


The departing Deputy Secretary of Transportation, John Porcari, wrote
a letter in the closing days of 2013 opposing the U.S. Air Force’s
announced plans to begin broadcasting Civil Navigation (CNAV)
message-populated L2C and L5 signals as early as April 2014. Military
personnel are incensed over what they see as Porcari’s impugning,
when not ignoring, the Air Force 35-year track record of broadcasting
the gold standard of global navigation satellite signals — something
in which Transportation has zero experience.

Porcari alludes in his December 27 letter to “non-standard
engineering tools” and “non-standard operations” that he believes
would come into play for early CNAV broadcast. “These have the
potential to inject human error, which may result in unacceptable GPS
constellation operation.”

What Porcari means by “non-standard” he does not specify, although he
confesses to unease as “the ability to monitor these signals,
[without which] the system will not know if the L2C and LS signals
are within specification. Given these risks, DOT is concerned that
the CNAV messages could provide hazardously misleading information,
impacting GPS safety-of-life, protection of property, and economic
security applications.” The full text of the Porcari letter is
available here.


See: http://gpsworld.com/dot-disses-dods-gps-chops/
  #2  
Old January 14th 14, 08:33 PM posted to sci.geo.satellite-nav
Sam Wormley[_2_]
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Posts: 775
Default DoT Disses DoD’s GPS Chops

DOT Letter to the Air Force
http://gpsworld.com/wp-content/uploa...orce_CNAV1.pdf


  #3  
Old January 14th 14, 09:46 PM posted to sci.geo.satellite-nav
Alan Browne
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Posts: 1,339
Default DoT Disses DoD’s GPS Chops

On 2014.01.14, 16:11 , Sam Wormley wrote:

See: http://gpsworld.com/dot-disses-dods-gps-chops/


http://gpsworld.com/wp-content/uploa...orce_CNAV1.pdf



A bit of a silly protest. While it's probably true that the "engineer"
cooked code that initially comes out, not having been validated and
tested completely may contain errors, receivers that can receive it will
likely not use any signal that has a not-for-navigation flag set. As
long as that (those) flags are well tested, then there's little danger.
I doubt, for aviation, that any TSO'd receivers are out there that
process L2C, even if they receive the signal, into the nav solution.
(Though they might output status/content of the L2C message).

It's germane to note that back in the early 90's before GPS was
completely online that GPS was pretty weak with respect to navigation
suitabilty for critical use (like airborne nav). Integrity monitoring
was a joke (you could be receiving a garbage ICD-200 message and it
would declare that sat healthy until a ground monitor noticed the issue
and set the bit. Even then delays of up to 4 hours were to be expected.

--
“Everybody has a plan until they get punched in the face.”
- Mike Tyson

 




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