Re: Has the USA ever verified GPS reliability?

On Aug 6, 12:30 pm, C J Campbell <christophercampb...@xxxxxxxxxxx>
wrote:

[snip]

Galileo
is supposed to be accurate to one meter, but it will not be operational
until 2012. By then all the GPS satellites will be GPS IIR-M and IIF,
which will be accurate to less than a meter.

Not to mention that (in the case of the IIFs), the second civil signal
(L5) is
in the ARNS band, so it will be approved for aviation safety-of-life
applications.
A big advantage of having the second frequency (besides redundancy),
is that
the receiver can now improve the Ionospheric error component.
Currently, this
requires augmentation.

It's not at all inconceivable that vertically guided approaches could
be provided
with a dual-frequency receiver.

[snip]

As for reliability, promoters of Galileo claim that they will have 30
satellites while GPS has only 24. This, of course, is highly
misleading. In fact, there are no operational Galileo satellites and
the GPS system hasn't been limited to 24 satellites in more than a
decade. There are currently 31 operational GPS satellites (the
information in AIM is outdated). I think that number includes the WAAS
satellites, but I am not sure.

The 31 birds are GPS birds only. The GEOs are not included in that
count.

While it's true that there haven't been as few as 24 in some time, my
under-
standing is that the spec. are still predicated on this minimal
constellation
deployed at IOC. The downside is that the availability (of Accuracy,
Continuity,
and Integrity) are actually much better than for which can be taken
credit. Hence,
a lot of the conservatism (read: error budgets) built into the
navigation services
currently being provided.

[snip[

As for accuracy testing, the United States Coast Guard has
responsibility for testing and operating GPS, not the FAA.

Do you have a reference for this? While they may be providing the
service, it is my understanding that USCG is under no contractual
agreement to be responsible for this.

DoD is responsible for monitoring the SIS. Although I believe they
still are
only are officially obligated to monitor the Military signals, they
understand
the value of being stewards of GPS, and this is evidenced in the
availability
of the signals provided to the Civil community.

FAA is responsible for monitoring WAAS, so in a sense they are
monitoring
it continuosly. The FAA Technical Center in ACY (http://
www.gps.tc.faa.gov/)
has been. in effect, 'testing' GPS for quite some time and has many
TBs of
SIS data to prove it.

[snip]

Waddling Eagle
World Famous Flight Instructor

Regards,
Jon

.

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