
Air-Traffic Control Is in the Midst of a Major Change from Radar to GPS - dsgerard
https://www.wsj.com/articles/air-traffic-control-is-in-the-midst-of-a-major-change-11579861800
======
jrockway
A lot of comments seem to be about spoofing. Remember that there are multiple
humans in the loop -- experienced pilots and experienced air traffic
controllers -- and multiple levels of redundancy. Pilots have access to
barometric altitude, radar altitude, traditional VHF navaids, TCAS-issued
resolution advisories (based on directional antennas, not GPS)... in addition
to GPS. Air traffic controllers have primary radar and secondary radar in
addition to ADS-B information.

You could probably cause a lot more trouble by buying an aviation radio off
the shelf and just chatting on the frequency or issuing fake clearances if you
want to be a mass murderer.

Ultimately the system comes down to many systems working together, not one
stream of commands between two computers.

~~~
FabHK
> buying an aviation radio off the shelf and just chatting on the frequency or
> issuing fake clearances if you want to be a mass murderer

Incidentally, I am happily surprised that that never seems to happen. One
could so easily create so much chaos at an airport... There is no
authentication whatsoever.

~~~
Patrick_Devine
The problem with _requiring_ authentication is that it can create a safety
issue when communications break down. As a pilot it's not a bad idea to carry
a spare handheld radio, or even use a cel phone, when you lose communications.

I was flying once with a buddy of mine who was Pilot-In-Command and we lost
(or thought we had lost) our radio on an IFR flight back into the Bay Area.
What had happened was the Push-to-Talk button on the yoke had become stuck and
we were transmitting the entire time while attempting to diagnose what was
wrong. This happened for about five minutes. Thankfully he had a handheld
radio in his flight bag, and when we turned it on we figured out really
quickly what was going on.

In that scenario, if we didn't have the handheld radio, it would have caused a
worse problem.

~~~
leetrout
Now I'm trying to remember if the radios have TX lights that would help show
that you are transmitting...

~~~
briandear
G1000/G3000 radios do. TX and RX

~~~
kitteh
G1000 will disable tx if you are transmitting for 35 seconds straight I think
as a way to mitigate a stuck mic.

------
code4tee
Radar isn’t going away. This article talks as if ADS-B is replacing radar,
which it’s not. It’s enhancing radar where radar coverage exists and providing
coverage on traffic where radar coverage currently does not exist (usually
lower altitudes away from major airports and over the ocean).

~~~
danaliv
Indeed. Not everyone even has to have ADS-B Out. You only need it if you’re
going into or over Class C or B airspace, in the Class B veils, Class E above
10,000 except below 2500 AGL, and in Class E over the Gulf of Mexico. That
leaves huge swathes of airspace—dare I say _most_ airspace in the US—where
ADS-B isn’t required. You could fly across the entire country without hitting
an ADS-B requirement. And the only way for ATC to see non-ADS-B aircraft is
radar.

~~~
lutorm
Except that is also the same airspace where ATC doesn't _have_ to see you. You
don't even need a transponder to fly in those areas.

~~~
danaliv
It’s not just about seeing you, it’s about seeing everyone around you too.
ATC’s job is to separate aircraft and they can’t do that if they can’t see
non-ADS-B aircraft. In fact just today I overheard an approach controller
vector an American Airlines jet around VFR traffic at 1700’. That VFR traffic
was in “non-rule” airspace, where ADS-B isn’t required. (I saw the jet and the
VFR traffic from my cockpit.) They won’t be able to do that without radar.

------
onepremise
I worked for a firm, which studied satellite navigation and implementation for
air traffic control, guidance, safety, and ILS. I don't think that will ever
happen. There are huge gaping issues with GPS, both WAAS and GBAS. It's very
unreliable, especially in bad weather. The old-school RF tower and ILS, which
used Carrier frequency pairings by the runway, are way more reliable and
propagate bad weather while guiding the plane into a runway. There's also been
ongoing issues with truckers, with GPS jammers, which drive by airports
impacting the quality of signal for planes coming into runway. Even the GPS
signal itself has latency and lag, which prevents the plane from making quick
adjustments for avoiding traffic and ILS guidance.

~~~
BeeOnRope
Why do truckers have GPS jammers?

~~~
burundi_coffee
You either didn't see the comma or you're joking

~~~
mft_
Don’t think they’re wrong in their interpretation. Why would a trucker
_without_ a GPS jammer driving by an airport cause an issue?

------
gryphonshafer
A valuable part of the ADS-B out mandate is that planes even as small as mine
(a.k.a. tiny) can cheaply (<200$US) pick up ADS-B in and display it on a
consumer tablet. My private airplanes now have pseudo radar. Not every
airplane in the air is broadcasting, but most are. This is a huge safety win.
Almost without exception I'll see airplanes on my tablet long before I have
visual on them.

~~~
sokoloff
Without ADS-B out on your airplane (which you don't have for <$200), you will
only pick up mode-C traffic in your area if there's another airplane nearby
with ADS-B out and coded to receive ADS-B in. You would then be
intercepting/"piggybacking" the traffic transmissions meant for that airplane.

[https://ipadpilotnews.com/2019/09/ads-b-traffic-when-does-
it...](https://ipadpilotnews.com/2019/09/ads-b-traffic-when-does-it-work-when-
does-it-not/)

[https://www.faa.gov/nextgen/programs/adsb/faq/#x8](https://www.faa.gov/nextgen/programs/adsb/faq/#x8)
You probably have a much large hole in your coverage than you thought.

~~~
ryandrake
Fortunately (unpopular opinion among pilots) the FAA is slowly phasing in
ADS-B out as required equipment. Starting Jan 1 of this year, you need to tx
ADS-B if you're anywhere you'd otherwise need a Mode-C transponder, including
around many airports.

~~~
sokoloff
Nit: Starting Jan 2

------
MereInterest
There was a talk at DEFCON about this in 2012 [1]. The main issue is a radar
system gets its information from ground-based measurements, while a GPS system
gets its information from air-based measurements that are later transmitted to
the ground station. This means that those reports can be spoofed, or lied
about, or absent entirely.

[https://www.youtube.com/watch?v=CXv1j3GbgLk](https://www.youtube.com/watch?v=CXv1j3GbgLk)

~~~
danesparza
Also: Spoofing is not theoretical. It has already been done:
[https://www.wired.co.uk/article/black-sea-ship-hacking-
russi...](https://www.wired.co.uk/article/black-sea-ship-hacking-russia)

~~~
supernova87a
Well, as in the beginning of wifi/cell networks and all such similar
technologies, their priority was to make a first adequate and reliable system
that reports position. And getting operators to adopt it. Defeating bad actors
was not a major requirement.

Maybe if it's shown to be a great practical problem, they'll address it. If
not, then no they won't. I'm guessing they won't.

------
griffinkelly
I very recently had my ADSB fail while flying in a piper arrow. I think its
probably good to have redundant systems in place, its a core to aviation to do
that with instruments. Also, the military jams GPS rather frequently for
exercises: [https://www.thedrive.com/the-war-zone/17987/usaf-is-
jamming-...](https://www.thedrive.com/the-war-zone/17987/usaf-is-jamming-gps-
in-the-western-u-s-for-largest-ever-red-flag-air-war-exercise)

~~~
opwieurposiu
Ah the piper arrow. Fond memories of many trips around florida and caribbean
in that plane as a kid.

It was my job to "help" with the navigation, using a paper chart and VOR/NDB
steam gauge instruments. Dad was able to teach 10yo me how to do this stuff,
but it was easy to confuse from/to or think you are tuned to station x when
actually you are on Y, etc. Particularly night VFR was hard to be sure you
were exactly where you thought you were. We did not fly over open water at
night.

Later we got a primitive GPS, no maps just waypoints and lat/lng. That thing
was so much easier to use it was night and day. Just dial in a 3 letter code
for your airfield, and you get range,bearing,eta.

GPS is a huge improvement to safety and convince, but if it goes out a night
or in bad weather there are gonna be some problems.

~~~
jandrese
If it goes out you're back to the old methods, but of course you're all rusty
on those old methods because you don't normally have to use them.

I've had kids ask me what we did before we had GPS and Google Maps and I tell
them that we got lost or turned around a lot more often.

------
ZguideZ
I was an ATC from 1990-1994 - we were using equipment from the 1960s then and
I've heard it hasn't gotten much better - granted I was in the Marines - not
the most high tech bunch, but still - we were civilian certified. I was never
scared to fly before I knew who the other controllers were - an upgrade will
be very welcome - except then you might freak out when you know who is
building the software...

------
mattlutze
If there's anyone in the air control technology industry here, I'm curious
what parts of this change get you really excited, and which parts get you
really nervous?

~~~
o-__-o
The cost. This affects general aviation as older planes will require avionics
upgrades. Otherwise I’m excited for the sheer amount of data that will be made
available to the public. Now you will be able to track all FAA registered
planes

~~~
throw0101a
> Now you will be able to track all FAA registered planes

Almost all.

If you're flying VFR you can put your transponder into an anonymous /
incognito mode (if it supports it):

* [https://www.avweb.com/aviation-news/faa-acts-to-preserve-ads...](https://www.avweb.com/aviation-news/faa-acts-to-preserve-ads-b-data-privacy/)

If you want IFR or flight following you'll have to de-anonymized, which is no
worse than it was before ADS-B.

~~~
o-__-o
Just out of curiosity, how are you anonymous when an Ads-b transponder will
respond to any request it receives?

Does incognito mode in your browser stop you from being tracked if e.g Google
or facebook can see every or almost all of your requests?

~~~
throw0101a
In _in cognito_ mode your transponder sends out a random ICAO ID when you
squawk 1200 instead of the personally identifiable one.

So people can see _that_ someone is in a particular place, but not _who_ that
person/plane is.

------
yingw787
To an extent, this sounds terrifying. The first thing that jumped to my mind
is that GPS be jammed or spoofed. In fact, the U.S. military in its shift away
from COIN to great power competition in possibly highly contested environments
is training to have less reliance on GPS:
[https://www.zerohedge.com/news/2018-01-26/usaf-begins-
massiv...](https://www.zerohedge.com/news/2018-01-26/usaf-begins-massive-gps-
blackouts-western-us-during-largest-ever-air-war-drill)

Radar can be jammed too, but I would guess the EM signature powerful enough to
track. I don't know if GPS jammers would have that issue.

On a positive note, I think this would pave the way towards integrating
commercial drone infrastructure into our airways a lot better!

~~~
adatavizguy
We still maintain Loran C[0]. Interesting to note receivers have been
developed to grab the radio signal from all available stations, up to 40, and
triangulate location with eLoran. It's a nice to have as backup to GPS however
I'm not sure if it is effective against jamming or spoofing. So, the navy
still teaches celestial navigation to officers. [1]

EDIT: Apparently Loran C was discontinued in 2010.

[0][https://en.wikipedia.org/wiki/Loran-C](https://en.wikipedia.org/wiki/Loran-C)
[1] [https://www.stripes.com/news/break-out-the-sextant-navy-
teac...](https://www.stripes.com/news/break-out-the-sextant-navy-teaching-
celestial-navigation-again-1.391219)

~~~
sokoloff
> We still maintain Loran C

What does "still maintain" mean in this context? My Loran-C receiver stopped
working years ago when we turned off the signals.

[https://en.wikipedia.org/wiki/Loran-C#Loran-
C_in_the_21st_ce...](https://en.wikipedia.org/wiki/Loran-C#Loran-
C_in_the_21st_century)

------
ufmace
Regarding posts about spoofing and maintaining radar, it was my understanding
that the radar sets that most ATCs used was not actually powerful enough to
get direct returns from commercial aircraft, and relied on amplifying
transponders to be able to see them. Supposedly only militaries operate radars
powerful enough to see aircraft directly. Can anyone who knows more confirm or
deny? If that's true, I guess we're already in a world were ATC info could be
spoofed.

~~~
jcrawfordor
In the US, ATC radar and military radar are one and the same - the FAA and the
Air Force share the Joint Surveillance System (JSS). So, while the JSS has
plenty of limitations (including plenty of areas with no coverage even in the
mainland US), it's designed to meet the military objectives of being able to
locate even non-cooperating aircraft.

The JSS is a descendant of the SAGE system developed during the Cold War to
detect soviet aircraft. It has a reduced equipment footprint, but this is
generally due to improving radar technology, coverage is similar and the
backend data processing systems are much more advanced. The majority of radar
sites belong to and are maintained by FAA but report directly to the Air Force
air combat system.

~~~
jessaustin
Is there any other entity that operates these sorts of radomes? On a regular
commute of mine, there is one owned by the federal government that has no sign
out front [0], but it's not listed on the JSS page [1].

[0]
[https://goo.gl/maps/KHTP7vruKvGyqQu66](https://goo.gl/maps/KHTP7vruKvGyqQu66)

[1]
[https://en.wikipedia.org/wiki/Joint_Surveillance_System](https://en.wikipedia.org/wiki/Joint_Surveillance_System)

~~~
jcrawfordor
It took a bit of digging... this is an FAA radar, but not JSS. It's a
secondary radar reporting to the Kansas City ARTCC, code ZQJN. Essentially, it
transmits an 'interrogate' message in response to which aircraft transponders
transmit information on the aircraft. This is the system that ADS-B is more or
less a direct upgrade from.

I'm not sure exactly what equipment is installed there, I found an older
report listing an ASR-8 at that location but that system is obsolete and
inconsistent with a newer list showing it as a secondary (SECRA) site only.

~~~
jessaustin
You're very knowledgeable! I've been curious about this for a while. The site
and equipment does seem well maintained, so I don't think it has been retired
yet.

------
capkutay
I hope we can finally see some improvements at SFO. The fact that the
slightest impact on visibility can cause 4-5 hour long delays is ridiculous.
the SF government has tirelessly blocked all attempts to fix the runways so
that planes can land in visibility conditions (fog/rain) with the promise that
technology would solve the problem.

~~~
briandear
The problem isn’t the airport. It’s the lateral separation requirements for
IFR aircraft on the ILS. Most airliners can land in 0-0, but you can’t do 0-0
landings on parallel runways with the ILS because of lateral separation
requirements.

There is also flow control that is from the FAA — under IFR the acceptance
rates are reduced.

The short answer isn’t that SFO isn’t “upgraded” but the rate of aircraft
acceptance is reduced under low visibility conditions per the FAA — and for
good reason, separation of aircraft.

Here is more explanation: [https://media.flysfo.com/media/sfo/media/weather-
operations-...](https://media.flysfo.com/media/sfo/media/weather-operations-
primer_0.pdf)

------
neonate
[http://archive.md/6rZFp](http://archive.md/6rZFp)

------
Merrill
>GPS JAMMING EXPECTED IN SOUTHEAST DURING MILITARY EXERCISE

>GPS reception may be unavailable or unreliable over a large portion of the
southeastern states and the Caribbean during offshore military exercises
scheduled between January 16 and 24.

[https://www.aopa.org/news-and-media/all-
news/2020/january/14...](https://www.aopa.org/news-and-media/all-
news/2020/january/14/gps-jamming-expected-in-southeast-during-military-
exercise)

------
rocqua
How long until radar becomes an afterthought, and we get an issue because a
transponder has failed?

~~~
knodi123
I took flight school a few years ago, and had to learn to tune in non-
directional radio beacons, and use VHF Omni-Directional Range tools for
navigation. I wasn't allowed to use the GPS until I demonstrated mastery of
the others.

Considering that, I suspect the aviation industry will keep both systems
working for a surprisingly long time.

~~~
Someone
This isn’t for pilots to know where they are, it’s for air traffic control to
know where planes are.

If GPS were to become the sole way to do the latter, every airplane would
effectively get an invisibility cloak that those who want to do evil can
activate (and even worse. Switching off the on-board transmitter is less scary
than spoofing signals)

Because of that, I would expect they keep using some way to detect planes that
don’t tell them where they are, or radios broadcasting “plane P is at X,Y,Z”
without a plane being there.

~~~
ceejayoz
> If GPS were to become the sole way to do the latter, every airplane would
> effectively get an invisibility cloak that those who want to do evil can
> activate...

This is already the case. Much of the civilian radar system already relies on
transponders to get a good fix on aircraft, via secondary radar. Primary radar
coverage (no transponder required) is much more limited. Turn off the
transponder and you'll largely disappear from ATC's screens.

ADS-B isn't new in this regard.

------
northerdome
Living in San Francisco, I've always been curious if GPS will eventually let
both SFO runways stay open in poor visibility conditions one widely adopted.
Does anyone know?

~~~
az656
Most approaches that large airliners are doing are already RNAV (GPS)
approaches. The reason they close the parallel runway is because of the
current ATC aircraft separation rules.

------
ForFreedom
Keep in mind that GPS is more govt controlled, so is GPS more reliable than
Radar?

------
JoeAltmaier
Lots of important cautions posted in this thread.

On the plus side, lots of opportunity to create cockpit displays, warning
devices etc to increase pilot safety!

~~~
JoeAltmaier
Really! I'm working a contract on a cockpit device now, for this new
requirement.

------
rhacker
> allowing more planes in the air

So that's a good thing? interesting.

------
Rochus
What's the point in posting an article which has a paywall? Does anyone have a
link which points to an open version of the article?

~~~
tux1968
Apparently WSJ is okay with you reading things if you request the content with
the correct incantations. There are a bunch of paywall bypass plugins for
Firefox that invoke the magic words. Here's one:

[https://addons.mozilla.org/en-CA/firefox/addon/read-ft-
wsj/](https://addons.mozilla.org/en-CA/firefox/addon/read-ft-wsj/)

------
GnarfGnarf
When the Kessler syndrome occurs, all transportation will grind to a halt.

The Kessler syndrome is when collisions between objects cause a cascade in
which each collision generates space debris that increases the likelihood of
further collisions.

[https://en.wikipedia.org/wiki/Kessler_syndrome](https://en.wikipedia.org/wiki/Kessler_syndrome)

~~~
akiselev
GPS satellites are in geosynchronous orbit, far above any threat of Kessler
syndrome and we won't have nearly enough material in orbit that occlusion of
the satellites would become a problem for centuries, if ever.

~~~
jessriedel
GPS satellites are indeed at much higher altitudes and thus well protected
from (highly speculative) worst-care Kessler syndrome scenarios, which occur
in low-Earth orbit (<2,000 km altitude). However, GPS satellites are not in
geosynchronous orbit (35,7000 km altitude) but rather operate in a medium
Earth orbit of about 20,000 km.

~~~
tialaramex
Indeed. The GPS birds zip around, a GPS device has to learn (traditionally
from GPS itself but downloading from the Internet is much faster if you have
Internet and these days most devices can do that) where the birds are in order
to turn its relative distance from each satellite into an absolute position on
the Earth's surface.

If you have an actual GPS app there's typically a diagnostic screen where can
see where the satellites are and see them arrive and disappear from your
perspective as they orbit.

------
coldcode
The same GPS the US Government reserves the right to reduce the precision when
they feel like it? Seems risky idea to assume they will never do this.

~~~
kevstev
Isn't low precision something like +/\- 15 feet? For ATC, that seems more than
good enough when they keep jets a mile+ apart. It just needs to be more
precise than radar.

~~~
Johnny555
The government claims that they won't enable selective availability any more
(which is less useful as a protective mechanism anyway since multi-protocol
receivers can use GPS / Galileo / GLONASS / Beidou).

But if SA was enabled:

 _Before it was turned off on May 2, 2000, typical SA errors were about 50 m
(164 ft) horizontally and about 100 m (328 ft) vertically_

[https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_...](https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Selective_availability)

