Big News -- WAAS GPS is Operational for IFR

"C J Campbell" wrote in message
...

I might point out that VORs are also inoperative at certain time in
certain
regions. The Mc Chord VOR has not worked in over a year, despite it being
an
important airway intersection. So what are you suggesting we use for
backup
navigation systems for the VOR?

The back to VOR will remain GPS -- and maybe NDB as well. Maybe keep Loran
as well and build hybrid GPS-Loran boxes with built-in redundancy.


I think GPS is terrific and I particularly am looking forward to percision
GPS approaches. I just think it makes no sense to decommission he VOR/ILS
system, and I think in the end that is exactly the conclusion the FAA will
be forced to make.


--
Richard Kaplan, CFII

www.flyimc.com

"Scott Moore" wrote in message
...

There are multiple GPS satellites making up the GPS system. That is the
exact same redundancy.

And it is not sufficient redundancy... it can be jammed locally and leave
the pilot with no navigation alternative.

The very fact that we have RAIM alerts shows exactly why GPS cannot be the
only remaining navigation system -- if all we have is GPS, what do we do
when we get a RAIM alert?

--
Richard Kaplan, CFII

www.flyimc.com

Please do not mis-attribute others' remarks to me. I did not post the quoted
material.

"Ray Andraka" wrote in message
...
| Nope, GPS for aviation is essentially one frequency with code modulation.
The
| receiver picks out the different satellites by correlating the code
sequence
| against the received signal. The code sequences are orthagonal, which
means they
| are enough different that you only get a strong correlation peak for the
one
| satellite that matches the code you are correlating against. The long
code
| sequences provide a very high processing gain, so the signals can be
buried in a
| good deal of noise, however it is relatively easy to jam the entire system
with a
| strong transmittter on the carrier frequency. This is what RAIM is all
about. It
| doesn't even have to be an intentional jammer: intermodulation from TV
transmitters
| in close proximity has caused local outages, for example.
|
| It would be much harder to jam the entire VOR band because the VOR
signals are
| transmitted at much higher power (3 orders of magnitude), and the VOR band
covers a
| wide frequency band relative to the frequency of the center of the band.
|
| Scott Moore wrote:
|
| C J Campbell wrote:
|
| Bull****. GPS also works using multiple satellites and multiple
frequencies.
| If you are going to propose that the entire frequency band for GPS be
jammed
| or otherwise corrupted, then the same thing would work across the entire
| VOR band as well.
|
| --
| --Ray Andraka, P.E.
| President, the Andraka Consulting Group, Inc.
| 401/884-7930 Fax 401/884-7950
| email
| http://www.andraka.com
|
| "They that give up essential liberty to obtain a little
| temporary safety deserve neither liberty nor safety."
| -Benjamin Franklin, 1759
|
|

"Richard Kaplan" wrote in message
...
|
| The back to VOR will remain GPS -- and maybe NDB as well. Maybe keep
Loran
| as well and build hybrid GPS-Loran boxes with built-in redundancy.
|
|
| I think GPS is terrific and I particularly am looking forward to percision
| GPS approaches. I just think it makes no sense to decommission he
VOR/ILS
| system, and I think in the end that is exactly the conclusion the FAA
will
| be forced to make.

The FAA has said repeatedly that it plans to use radar to back up GPS. The
reason the FAA is so hot to decommission all the other radio navaids is that
they are far too expensive and the cost is spread across a very small user
base, whereas the cost of GPS is shared by all segments of society.

"C J Campbell" wrote in message
...

"Richard Kaplan" wrote in message
...
|
| The back to VOR will remain GPS -- and maybe NDB as well. Maybe keep
Loran
| as well and build hybrid GPS-Loran boxes with built-in redundancy.
|
|
| I think GPS is terrific and I particularly am looking forward to
percision
| GPS approaches. I just think it makes no sense to decommission he
VOR/ILS
| system, and I think in the end that is exactly the conclusion the FAA
will
| be forced to make.

The FAA has said repeatedly that it plans to use radar to back up GPS. The
reason the FAA is so hot to decommission all the other radio navaids is
that
they are far too expensive and the cost is spread across a very small user
base, whereas the cost of GPS is shared by all segments of society.

Then there is the value all that VHF navigation bandwidth. Perhaps FAA
could use the cash for somehting useful.

John P. Tarver, MS/PE

Peter wrote:

Scott Moore wrote

I don't have
the ability to evaluate GPS jamming, nor VOR jamming,

Then you should read up on the subject, and the Volpe report on GPS
vulnerability is a good start. I did have a URL for it but the
institute has moved it somewhere else. I have it archived (PDF) so if
you email me I can give you a private URL for it or email you a copy.
Or someone can post a new URL if they can find it; I am 100% sure it
is online.


Fine, you have a study. What we need is an unbiased comparision of
the vulnerabilities of GPS to the vunerabilities of VOR. That is all
that really makes the decisions here, because (again) there is no point
claiming that GPS is more vulnerable than VOR without such a study.

As others have explained, GPS can be jammed very easily, over a wide
area (of the order of 500 miles radius) whereas jamming more than one
VOR is a lot harder and the effect would be only localised; it would
need large amounts of power and most probably separate transmitters to
jam multiple VORs. This is just elementary electronics and signal
processing.

GPS jamming is localized as well. A ground based transmitter has perhaps
30 miles of horizon to jam (derived from a tangent line from the earth
and math). More altitude can jam farther (hence the "jammer on a ballon"
theory), but lets save time here -- both services are line of sight, so
they are both going to have similar jamming profiles. Everyone agrees
that it would take more power to jam VOR, but all this really does is
make the "$100 radio shack ballon" jammer appear shocking. There is no
material barrier to making a VOR jammer.


As I mention elsewhere, there are techniques to make a GPS receiver
relatively immune to jamming - especially if one is working on the
assumption that the jamming signal is just a crude carrier-wave
transmitter and that the transmitter is ground (not space) based. For
example, combining a GPS receiver with an INS (e.g. FOG based) enables
the receiver to cope with a much poorer GPS signal. You can read about
these in the above reference. These techniques are not AFAIK
commercially available, presumably for the same reasons that all
commercial GPS receivers are required to be limited to 60,000 feet
altitude in their firmware.

And, as another poster pointed out, GPS antennas are pointed at the sky,
whereas VORs cannot be so directional.

Lets back up a step. The widest deployment of GPS is in light aircraft.
Airliners don't really use it yet, and even when they do, they have
INS redundancy. The bottom line is that the most attractive target for
terrorists, the airlines, is the most unlikely one to be affected by
any jammer, VOR or GPS.

It is that fundamental fact that I believe causes the "GPS haters" to
constantly flip back and forth between talking about terrorists and
talking about other types of interference. The terrorist idea makes good
(shocking) headlines, but would be a stunningly ineffective method
if actually put into use.

Nobody in this thread ever asked me if I am for shutting VORs down.
I am not. I have a 430, which has VOR built in, and another VOR besides
that, and I am perfectly happy with it as a backup method.

But what seems to happen here as regular as clockwork is that someone
reads a "shocking" headline about radio shack GPS jamming and runs
around ranting about GPS "insecurities". I am all for a *rational*
comparision about the reliability and risks of GPS vs. VOR or any
other service. I am all *against* the chicken-little rantathon
that is getting so much play in the press and here as well. If someone
comes running down here yelling about GPS jamming, be prepared to talk
about jamming of VOR or other services as well. Otherwise its just
a **** flinging contest.


Peter.
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"C J Campbell" wrote in message
...

WAAS is offering approaches where there are none now, so the GPS is giving
me an option where none existed before. A RAIM alert does not disable your


I think GPS and WAAS are both very desirable in the National Airspace
System -- no one is arguing otherwise.

The point is simply that we cannot realistically have an airspace system
with nothing but GPS for navigation.

There are ways for GPS to be jammed over a wide enough area to prevent
having a realistic alternate, either intentionally or otherwise.

There have also been GPS NOTAMs prohibiting enroute operations over various
regions.

All of aviation is predicated on having a "Plan B" - Dismantling the VOR/ILS
system will leave pilots with no Plan B except radar vectors and ASR
approaches, and that just does not seem realistic or desirable to me.


--
Richard Kaplan, CFII

www.flyimc.com

"Richard Kaplan" wrote in message
...
|
|
| Besides, all current proposed GPS approaches will have minimums higher
than
| standard 200 - 1/2 ILS minimums -- it is unclear if WAAS GPS will EVER be
| able to go down to 200 - 1/2 although it may come close, like perhaps
350 -
| 3/4. Do you really think current airports with ILS approaches will react
| calmly to decommissioning their ILS systems to they get higher minimums on
| their new GPS precision approaches?
|

The original announcement says that approach minimums will be as low as 250
if the airport can certify that it is clear of obstructions and has the
required approach lighting. An airport that already has an ILS should meet
those requirements. Ultimately, WAAS is supposed to give much lower minimums
than that.

I think it will take far less than 10-20 years to convince most of the
knee-jerk "Itcan'tbedone.Itwon'twork" crowd. The troglodytes usually come
crawling out of their caves when they find their anti-innovation attitude is
costing them business. Then again, a significant part of the population
still believes that we should not be flying in the first place.

"C J Campbell" writes:

I think it will take far less than 10-20 years to convince most of
the knee-jerk "Itcan'tbedone.Itwon'twork" crowd. The troglodytes
usually come crawling out of their caves when they find their
anti-innovation attitude is costing them business.

I don't remember any of that in this thread. People have suggested
that (a) GPS needs ground-based backup like VOR, NDB, or LORAN for
safety, (b) other countries have trouble relying exclusively on a
system controlled by the U.S. military, and (c) the transition will
take a while, but I don't remember any postings claiming that GPS
precision approaches cannot or will not work -- everyone seems to be
looking forward to them.


All the best,


David

--
David Megginson, , http://www.megginson.com/

Richard Kaplan wrote:

Again, GPS and WAAS are great, but no way are other approach types going to
all disappear.. we may lose a few enroute navaids but VOR and especially ILS
are here to stay for a long, long time.


10 years is probally an accurate estimate. That will be enough time to place
higher power satellites in orbit, and for airlines and busjet outfits to work
out their backup procedures to their satisfaction with INS.

After that it will be GA pilots and the AOPA lobbying to keep VOR in use, and
AOPA's heart is not really in the fight (being a GPS/WAAS avocate all these years).
That leaves "us" with about the clout of a sparrow on bad berries. Oh, and I won't
be joining you, nor I suspect will many other pilots. Four course ranges didn't
survive as VOR backups, either.

I'll predict: massive decommissioning around 2010.

--
For most men, true happiness can only be achieved with a woman.
Also for most men, true happiness can only be achieved without a woman.
Sharp minds have noted that these two rules tend to conflict.....