On Oct 25, 3:23*pm, macpacheco <marc...@macp.eti.br> wrote:
> On Oct 25, 7:20*pm, GPSGUY <sat_ali...@yahoo.com> wrote:
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> > On Oct 22, 3:28*pm, macpacheco <marc...@macp.eti.br> wrote:
>
> > > On Oct 22, 7:33*pm, GPSGUY <sat_ali...@yahoo.com> wrote:
>
> > > > On Oct 22, 10:44*am, Alan Browne <alan.bro...@FreelunchVideotron.ca>
> > > > wrote:
>
> > > > > On 2011-10-22 13:34 , Alan Browne wrote:
>
> > > > > > On 2011-10-22 11:52 , HIPAR wrote:
> > > > > >> at Newark (thanks GPSGUY) and the never ending Lightsquared fiasco.
>
> > > > > > The issue of "privacy jammers" has gone way up the flagpole in the last
> > > > > > year or so. They will catch some trucker with one and they willfine him
> > > > > > and jail him "pour encourager les autres." Airport police (of whatever
> > > > > > stripe) could be equipped with detectors to help apprehend them.. And
> > > > > > customs agents will need to be educated in stopping these at the border
> > > > > > and imposing stiff fines on importers and brokers.
>
> > > > > > These jammers hit the GPS signal, not the LAAS signal.
>
> > > > > Sorry - should have written as I did in my reply to GPSGUY:
>
> > > > > ***
> > > > > LAAS receivers use survey style choke ring GPS antennas that are good at
> > > > > rejecting spurious, low elevation, low power jamming signals thatwould
> > > > > come from "privacy jammers" located on the adjacent highway. *Indeed in
> > > > > a lot of cases there would not even be line of sight to the LAAS antenna.
>
> > > > > Aircraft GPS are more susceptible because the antennas are open windows
> > > > > and up in "free space".
> > > > > ***
>
> > > > > --
> > > > > gmail originated posts filtered due to spam.
>
> > > > I guess we can debate the affect of jammers on different GPS
> > > > technologies, but the LAAS program is still dead, at least with GPSas
> > > > the primary nav aid. That's a fact.
>
> > > I wish LAAS was dead. But it doesn't seem to be. Its already
> > > operational for CAT I (useless since CAT I can be done with SBAS today
> > > in countries that have coverage), the FAA seems bent on moving forward
> > > with LAAS. LAAS makes sense for countries that don't intend to have
> > > their own SBAS and don't want to be part of WAAS, EGNOS, MSAS, ... for
> > > political reasons. But since LAAS is installed for around 25nm
> > > coverage radius, it has been deployed on just a few airports where
> > > there's financial sponsorship, as a showcase for nationwide
> > > deployment. And so far the system installed in Newark-NJ hasn't been
> > > used for JFK or LGA. If even that's not possible, then LAAS will cost
> > > at least twice as planned.
>
> > > I argue that its cheaper to continue using current ILS systems for CAT
> > > II/III systems until GPS L5 is FOC and Galileo is IOC, then with GPS
> > > dual frequency FOC, GLONASS dual frequency FOC + Galileo dual
> > > frequency IOC, it should be cheaper to use SBAS for CAT II and require
> > > enhanced synthetic vision for CAT III (with SBAS guiding the aircraft
> > > until CAT II minimums, requiring enhanced synthetic vision ground
> > > contact at that point). Throw some money around 2014/2015 for USAF to
> > > start 4 launches yearly until GPS L5 is FOC, that will be a much
> > > better use of that money.
>
> > > WAAS is proven to have performance levels barely adequate for CAT II
> > > today (but with IONO calculations performed on a grid basis, and
> > > without GLONASS nor Galileo), with IONO calculations at the receiver's
> > > aircraft and three constellations available, it should be good for at
> > > least CAT IIIa (50ft DH), and synthetic vision can take it from there
> > > to the ground. With dual frequency, triple (or quadruple)
> > > constellation SBAS, CSAC clocks at the receiver+INS for integrity
> > > monitoring, I'm sure CAT IIIb will be possible even without synthetic
> > > vision. INS would be used for acceleration measurements only,
> > > comparing position deltas and CSAC for comparing GNSS time deltas, if
> > > there's a jamming / spoofing scenario, INS+CSAC will catch it
> > > instantly with a large jump in either.
>
> > > The issue is the FAA is ultra, ultra, ultra conservative, and can't
> > > look forward to enhanced synthetic vision's full potential. I
> > > understand they're afraid to certify relatively new technology for
> > > such critical usage, but let's face, it's been used by military
> > > aircraft for 30 years for low level IFR flying. It's just made it into
> > > civilian aircrafts recently. If you never heard of it, just google
> > > LANTIRN.
>
> > > Marcelo
>
> > Ok, let's see where LAAS is in a year, two years, three years. The FAA
> > is not moving forward with LAAS. It's dead. There's still some budget
> > and activities but they are winding down, not spooling up.
>
> > You're right in that the FAA is ultra, ultra, ultra conservative. If
> > you agree, then why would they roll out a system as venerable as GPS-
> > based LAAS?
>
> > APNT is the where LAAS is headed, if at all. Which "A" that is remains
> > to be seen.
>
> The issue with LAAS is cost, not vulnerability. WAAS is just as
> vulnerable to localized jamming. WAAS was never identified as
> vulnerable since there was no ground system monitoring WAAS integrity
> at Newark at the time, while LAAS has that feature. And WAAS is fully
> deployed, with all billions of US$ already spent, and giving
> measurable return to its users, while LAAS would require a ton of
> money for a nationwide roll out. The main bottleneck before WAAS money
> is paid by just decommissioning thousands of ILS installations at
> small/medium city airports is the lack of the L5 signal, which would
> make WAAS a lot more robust (invulnerable from single frequency
> jammers).
>
> But the root cause isn't either system per se, it's the 60-100W signal
> transmitted by any space GNSS system, that upon reaching the surface
> is down to less than 0.1W, any signal this weak is extremely
> vulnerable to jamming, a 1W jammer is easy to power with a car's
> battery for days and will totally jam civilian GNSS signals up to
> hundreds of feet and cause major interference up to a mile within line
> of sight, and I'm very likely underestimating those ranges.
>
> Even today it's completely unfeasible today to broadcast a 1000W
> signal from a satellite and even that wouldn't be enough to power
> through a basic 10W jammer at close range (when the signal reaches the
> ground). As long as there's a power source, jammers up to thousands of
> Watts are available, those disrupt all GPS signals essentially limited
> only by line of sight (up to hundreds of miles airborne). And airborne
> jammer of 1000W radiated power could jam other airborne sensors as far
> as a thousand miles away depending on the altitude of both jammer and
> jammed entities. And replace that 10W jammer with a 10W spoof
> transmitter, and trouble multiplies, since its better to be unable to
> receive a GPS signal than to think you're receiving a good signal that
> causes aircraft to crash in bad weather.
>
> Instead, the current and previous administration decided to
> essentially ignore the threat (at least publicly) and in the case of
> the Obama administration, killing eLoran research and the Loran-C
> infrastructure destroyed the easiest means to provide with a great
> backup that would provide a very powerful signal on a completely
> different frequency from all GNSS signals. eLoran would have broadcast
> signals as strong as 100KW from a ground antenna, that would have been
> about 4 orders of magnitude more powerful than a GNSS signal even a
> thousand miles away from the towers.
>
> The other alternative to eLoran, L5 pseudolites would reuse the
> existing DME installation infrastructure by extending it. Current DME
> systems already broadcast in the L5 band at power levels that would
> rival most jammers, and by placing one pseudolite at each one of the
> worlds critical DME sources, it would essentially kill the jam threat
> for major airports (since those have multiple DMEs in sight even at
> low altitudes). Since a ground based L5 signal would not suffer from
> IONO effect, and its high power would help with multipath issues, its
> ranging accuracy would be significantly better than GPS signals.
> Finally pseudolites are already commercially available, the main
> difference is they operate in other bands. Add the recent
> affordability of chip scale atomic clocks, and L5 pseudolites could be
> a killer combination against the thread of GPS jammers and spoofs. And
> by carefully adding DME pseudolites to all airports with any CAT I
> approach would maintain at least LP(Localizer performance) and RNP 0.3
> approaches at those airports, even in face of some serious GPS
> jamming.
>
> Again, my issue with LAAS isn't its technical ability to deliver CAT
> III approaches, it might require the GPS L5 signal operational to get
> there, but it will eventually deliver, the real question is its cost,
> considering that with the GPS L5 signal (arguably) WAAS will deliver
> CAT II approaches and with triple constellation + dual frequency WAAS
> will be able to deliver CAT IIIa approaches (or even CAT IIIb). So if
> WAAS/SBAS delivers CAT IIIa, what's the point in having GBAS at all ?
>
> It boils down to politics. The current democratic administration
> decided it was more important to use the Loran C as a political
> example of cost cutting, should they decommissioned the infrastructure
> without destroying it, eLoran development could have moved on, and
> eLoran could have been refined to completely eliminate unnecessary
> aspects of Loran C, leaving eLoran as directly comparable to GPS as
> possible and adding WAAS corrections to its broadcast, since the L1 C/
> A WAAS signal is harder to receive than the GPS L1 C/A signal (250bps
> versus 50bps and the GEOs fly higher in the sky, reducing both the
> signal strength received and the SNR margins required to decode,
> specially at higher latitude).
>
> The other very interesting suggestion was floated by gpsworld.com, and
> its adding GPS jammer/spoof detectors to all future smartphones, ...
>
> read more »

Well, no. The reason it was killed was venerability. Budget was an
issue, but the Newark incident was the nail in the coffin. A vote of
no confidence.

I don't know what you mean by WAAS integrity not being monitored
during the Newark incident. That's an odd statement. The Newark
incident was relatively recent and WAAS was fully operational at that
time. It's been like this http://www.nstb.tc.faa.gov/RT_WaasSatelliteStatus..htm
for years.

GPS/WAAS was likely jammed in some inbound/outbound instrumentation
too, but disabling LAAS is a much different animal than WAAS,
especially from a political perspective. No one wants to be
responsible for a precision landing system that drove a plane into the
ground.

On Oct 26, 2:28*am, GPSGUY <sat_ali...@yahoo.com> wrote:
> read more »

What I mean is WAAS is unable to detect jaming/spoofing far from the
reference stations.
The closest reference station to Newark I believe is in New York
center close to the Long Island ISLIP airport, perhaps 20 miles away,
even a 10W jammer at ground level wouldn't be noticed at all 20 miles
away at ground level, due to the curvature of the earth.
I'm not sure how WAAS would react to jamming affecting a single
reference station, it shouldn't flag all satellites in view as bad,
since other reference stations would be receiving a good signal.
WAAS and EGNOS are designed to be able to operate over a huge
geographical area, for instance in the future there might be reference
stations in Argentina and Chile, adding to the measurements made as
far north (and west) as Alaska, so one reference station with signal
trouble shouldn't bring the whole system down (which would effectively
happen if a whole bunch of satellites were flagged as faulty). EGNOS
today has reference stations in Norway and South Africa (over 10000
miles away).
LAAS on the other hand is a local system, designed to cover perhaps a
25x25 nautical mile area, so a fault in one LAAS system wouldn't be
quite as dramatic as in WAAS.

Marcelo Pacheco

> What I mean is WAAS is unable to detect jaming/spoofing far from the
> reference stations.
> The closest reference station to Newark I believe is in New York
> center close to the Long Island ISLIP airport, perhaps 20 miles away,
> even a 10W jammer at ground level wouldn't be noticed at all 20 miles
> away at ground level, due to the curvature of the earth.
> I'm not sure how WAAS would react to jamming affecting a single
> reference station, it shouldn't flag all satellites in view as bad,
> since other reference stations would be receiving a good signal.
> WAAS and EGNOS are designed to be able to operate over a huge
> geographical area, for instance in the future there might be reference
> stations in Argentina and Chile, adding to the measurements made as
> far north (and west) as Alaska, so one reference station with signal
> trouble shouldn't bring the whole system down (which would effectively
> happen if a whole bunch of satellites were flagged as faulty). EGNOS
> today has reference stations in Norway and South Africa (over 10000
> miles away).
> LAAS on the other hand is a local system, designed to cover perhaps a
> 25x25 nautical mile area, so a fault in one LAAS system wouldn't be
> quite as dramatic as in WAAS.
>
> Marcelo Pacheco

Oh, I see, jamming the WRS (such as LightSquared).

Well, I'm not sure it makes a difference to the inbound/outbound
aircraft because it's not going to work either way.

Jamming the WRS will likely cause a regional WAAS outage, unless
you're in a location like Alaska where the WRS density is high.

Good luck on WRS in South America. GPS users would love it, but it
will never happen. They're stuck with commercial subscription services
and a spotty 283khz broadcast.

On Oct 27, 12:22*am, GPSGUY <sat_ali...@yahoo.com> wrote:
> > What I mean is WAAS is unable to detect jaming/spoofing far from the
> > reference stations.
> > The closest reference station to Newark I believe is in New York
> > center close to the Long Island ISLIP airport, perhaps 20 miles away,
> > even a 10W jammer at ground level wouldn't be noticed at all 20 miles
> > away at ground level, due to the curvature of the earth.
> > I'm not sure how WAAS would react to jamming affecting a single
> > reference station, it shouldn't flag all satellites in view as bad,
> > since other reference stations would be receiving a good signal.
> > WAAS and EGNOS are designed to be able to operate over a huge
> > geographical area, for instance in the future there might be reference
> > stations in Argentina and Chile, adding to the measurements made as
> > far north (and west) as Alaska, so one reference station with signal
> > trouble shouldn't bring the whole system down (which would effectively
> > happen if a whole bunch of satellites were flagged as faulty). EGNOS
> > today has reference stations in Norway and South Africa (over 10000
> > miles away).
> > LAAS on the other hand is a local system, designed to cover perhaps a
> > 25x25 nautical mile area, so a fault in one LAAS system wouldn't be
> > quite as dramatic as in WAAS.
>
> > Marcelo Pacheco
>
> Oh, I see, jamming the WRS (such as LightSquared).
>
> Well, I'm not sure it makes a difference to the inbound/outbound
> aircraft because it's not going to work either way.
>
> Jamming the WRS will likely cause a regional WAAS outage, unless
> you're in a location like Alaska where the WRS density is high.

There's no grid mask to indicate localized/regional jamming in SBAS.
There's no means at all in SBAS to inform users of localized signal
troubles.
Per satellite there's a status flag (UDRE level, 3, 3.75, 4.5, 5.75,
7, 15=precision approach, 50/150=Non precision approach, 175=Not
monitored, 200=Do not use), clock correction, orbit correction, and
some ancillary data, but there's NO indication of localized jamming in
effect (which would apply to all satellites in that area).
The only grid like information is the IONO corrections grid, but the
IONO grid is used for users far, far away, since the IONO grid is used
per satellite depending on the 3D line from the user and an individual
satellite, for instance, a user in Chicago receiving a satellite over
Miami would use the IONO grid around Atlanta (not precisely, just for
understanding purpose) for that satellite.

> Good luck on WRS in South America. GPS users would love it, but it
> will never happen. They're stuck with commercial subscription services
> and a spotty 283khz broadcast.

The main bottlenecks are L5 and nationalistic reasons. Technically for
users far south (away from the iono scintillation areas in the
equatorial/sub equatorial areas), WAAS would work extremely well, even
with just 6 stations plain LPV (250ft DH) and LP would be easy to
achieve. The main reason an expansion of WAAS farther south hasn't
happened yet is the lack of the L5 signal which prevents most of
Central/South America from using an eventual WAAS expansion due to
iono scintillation. With L5, with as little as a dozen WAAS stations
throughout South America and Central America, LPV200 performance would
be available all over the place, since IONO corrections could then be
done on the receiver. In the future if you require all SoL SBAS users
to have dual frequency capability, all it would take is 30 reference
stations for worldwide SBAS coverage, since the main requirement for
station density is IONO corrections. For instance with L5 GPS, a
station in Colombia and one in French Guyana in addition to the
already available WRS roster would bring coverage to the entire
central america / caribean for dual frequency users.

For the cost of 6 LAAS stations, about a dozen WAAS stations could be
added, since each WAAS station doesn't need a half a dozen reference
receivers like LAAS uses, over a 20 year span, the largest cost item
would be data transmission links back to the US for centralization of
the measurements, but that's not much (a WAAS station shouldn't
generate more than 64kbps of data, and multiple stations could be
aggregated nationally to lower international link costs). So with the
cost to bring GBAS to just 4 of South America's 30+ major airports,
full coverage would be achieved.

But the main reason is the same Europe wants Galileo, South America is
in average even more distrustful of the US. However, adding SBAS
maintaining most ILS as backups wouldn't make South America dependent
on the US, SBAS could be just one alternative, and would bring CAT I
approaches to hundreds of airports that will never get a CAT I system
here. My home town with close to 2 million people received on CAT I
system that should be deployed in the next year or so, in the US a
city 10% that size has ILS approaches and a city that size would have
2-6 CAT I systems (one for each end of the main two or three runways).

SBAS ROI is clear, and its 100% worthwhile:
Even without L5 operational, by 2020 50% of North America's lowest
utilization ILS CAT I and 1/3 of VOR/NDB beacons could be retired
With L5 operational, 80% of ILS CAT I systems and all NDB plus all non-
essential VOR/DME beacons could be retired
That alone is worth half a billion dollar in yearly savings.
The 2020 date is an approximation, considering there are still
2000-3000 approaches that need to be developed/updated for full WAAS
utilization.

Remember that public SBAS reason for being is aviation, all other
users are secondary with the aviation requirement, there would be no
WAAS or EGNOS.

Marcelo Pacheco

> There's no grid mask to indicate localized/regional jamming in SBAS.
> There's no means at all in SBAS to inform users of localized signal
> troubles.
> Per satellite there's a status flag (UDRE level, 3, 3.75, 4.5, 5.75,
> 7, 15=precision approach, 50/150=Non precision approach, 175=Not
> monitored, 200=Do not use), clock correction, orbit correction, and
> some ancillary data, but there's NO indication of localized jamming in
> effect (which would apply to all satellites in that area).
> The only grid like information is the IONO corrections grid, but the
> IONO grid is used for users far, far away, since the IONO grid is used
> per satellite depending on the 3D line from the user and an individual
> satellite, for instance, a user in Chicago receiving a satellite over
> Miami would use the IONO grid around Atlanta (not precisely, just for
> understanding purpose) for that satellite.
>
> > Good luck on WRS in South America. GPS users would love it, but it
> > will never happen. They're stuck with commercial subscription services
> > and a spotty 283khz broadcast.
>
> The main bottlenecks are L5 and nationalistic reasons. Technically for
> users far south (away from the iono scintillation areas in the
> equatorial/sub equatorial areas), WAAS would work extremely well, even
> with just 6 stations plain LPV (250ft DH) and LP would be easy to
> achieve. The main reason an expansion of WAAS farther south hasn't
> happened yet is the lack of the L5 signal which prevents most of
> Central/South America from using an eventual WAAS expansion due to
> iono scintillation. With L5, with as little as a dozen WAAS stations
> throughout South America and Central America, LPV200 performance would
> be available all over the place, since IONO corrections could then be
> done on the receiver. In the future if you require all SoL SBAS users
> to have dual frequency capability, all it would take is 30 reference
> stations for worldwide SBAS coverage, since the main requirement for
> station density is IONO corrections. For instance with L5 GPS, a
> station in Colombia and one in French Guyana in addition to the
> already available WRS roster would bring coverage to the entire
> central america / caribean for dual frequency users.
>
> For the cost of 6 LAAS stations, about a dozen WAAS stations could be
> added, since each WAAS station doesn't need a half a dozen reference
> receivers like LAAS uses, over a 20 year span, the largest cost item
> would be data transmission links back to the US for centralization of
> the measurements, but that's not much (a WAAS station shouldn't
> generate more than 64kbps of data, and multiple stations could be
> aggregated nationally to lower international link costs). So with the
> cost to bring GBAS to just 4 of South America's 30+ major airports,
> full coverage would be achieved.
>
> But the main reason is the same Europe wants Galileo, South America is
> in average even more distrustful of the US. However, adding SBAS
> maintaining most ILS as backups wouldn't make South America dependent
> on the US, SBAS could be just one alternative, and would bring CAT I
> approaches to hundreds of airports that will never get a CAT I system
> here. My home town with close to 2 million people received on CAT I
> system that should be deployed in the next year or so, in the US a
> city 10% that size has ILS approaches and a city that size would have
> 2-6 CAT I systems (one for each end of the main two or three runways).
>
> SBAS ROI is clear, and its 100% worthwhile:
> Even without L5 operational, by 2020 50% of North America's lowest
> utilization ILS CAT I and 1/3 of VOR/NDB beacons could be retired
> With L5 operational, 80% of ILS CAT I systems and all NDB plus all non-
> essential VOR/DME beacons could be retired
> That alone is worth half a billion dollar in yearly savings.
> The 2020 date is an approximation, considering there are still
> 2000-3000 approaches that need to be developed/updated for full WAAS
> utilization.
>
> Remember that public SBAS reason for being is aviation, all other
> users are secondary with the aviation requirement, there would be no
> WAAS or EGNOS.
>
> Marcelo Pacheco

I'd say the main bottleneck is cost. If cost wasn't an issue, So.
America would have an SBAS today.

The iono is more dynamic in So. America, but you can say the same with
India and it's working for them. For that reason, I don't think L5 is
the major holdup.

The SBAS equipage ROI isn't that convincing. If it was, Boeing
wouldn't be balking.