Missing ADS-B Traffic Data?

ssokol

ssokol

Filing Flight Plan
Joined
Jul 29, 2013
Messages
21
Location
Kansas City
Display Name
Display name:
ssokol
I've had a number of FlightBox / Stratux users contact me regarding missing traffic data - aircraft that are observed visually or on systems like TIS or TCAS but which never appear on ADS-B. I spent a good chunk of this past weekend researching and testing and it turns out that they're right. But the problem isn't the receiver. It appears to be the ADS-B network itself.

I did a detailed write up of the testing and the results:https://www.openflightsolutions.com/the-case-of-the-missing-traffic/

I would love to get somebody to replicate the experiment and see if they get the same results. If you happen to have two ADS-B receivers and a friend who's willing to play along, please give it a try and see what kind of results you get.
 
You either have to be sending ADS-B Out, or be near another Out equipped aircraft to "light up" the traffic reporting for ADS-B In.
 
My understanding, and I may be wrong. Even if you are ADS-B Out, there is a code marker in the data that you send that you can handle ADS-B In data. Otherwise, they don't transmit it because it would be a waste.

I flew yesterday with my Statux set up to ForeFlight. While on the ground at VGT (North Las Vegas, NV) I could see all of the traffic on the ground at LAS. I do not have ADS-B Out, but others on the ramp must have both out and in.

Shortly after departure, I was near no other aircraft and lost all traffic displays. Through Red Rocks, west of LAS, to Goffs VORTAC, GFS, to Needles EED, a couple of approaches at KEED and into Lake Havasu, HII. No traffic seen.

Returning to VGT via EED, to VPVGM (east of Nellis) and into VGT. No traffic seen, even though we were under the LAS approach corridor, but well below any hockey puck airspace for and adsb equipped airliners.

I only have 978UAT freq set up. We did get weather updates, METARs, while returning for VGT, LAS, and BVU and Nellis AFB. Getting into the traffic pattern at VGT on a normal Slam Dunk arrival, I put the iPad down and did not check for any traffic displays.

I'm about ready to order one of the openflight boxes to get both freqs and GPS. My iPad is wifi only so no internal GPS. I'm using BadElfPro.
 
If ADSB is really for saftey why do they make it difficult to receive signals like this?
 
What the OP found is consistent with my experience too, and I have ADS-B Out as well as In. This is in fact what I have suspected for some time. My setup is a Garmin GDL-90 feeding a GMX-200. A number of times ATC has pointed out traffic to me, or I have acquired traffic visually without their help, that does not appear on my screen. The traffic that I see but do not know if ATC does, is not surprising since for all I know, those aircraft do not even have Mode C. But the traffic that is pointed out to me that I cannot see via ADS-B does not make sense if the GBTs are transmitting all of the traffic being seen by ATC's radar. It is not that I am out of range of a GBT as at least some of the time, I am seeing other traffic on my screen - just not the one that was called out to me. I thought perhaps it was that my GDL-90 is not truly ADS-B Out compliant (a known, and very disappointing, problem), but in view of the findings reported in the OP's article, I believe that explanation is inadequate and would very much like to know what is actually going on.
 
There were two nearby planes that did not show up on ADS-B for me last Sunday; not on the 750 or WingX. I saw one, but not the other. Meanwhile ADS-B had planes far from me showing up on WingX. ATC notified me about them as I was on an IFR flightplan. I did see two earlier nearby flights on ADS-B, both on the 750 and WingX, so hit-and-miss.
 
I look at it this way...no technology is perfect. It is supposed to be an AID to situational awareness and I consider any traffic I see on the screen as a bonus, not a definitive absolute picture of what is actually out there...and I am ADS-B Out.

Heck, I have had close calls while on Flight Following for traffic that ATC never called out. Eyes first and foremost, everything else just helps the eyes where to additionally look.
 
James331 said:
If ADSB is really for saftey why do they make it difficult to receive signals like this?
Click to expand...

US made it complicated by introducing two systems. The rest of the world uses 1090 and doesn't need all this In/ Out crap. FAA did 978UAT to throw a bone to GA to support the ATC upgrades. Then to force you to get the upgrade, they said you have to have UAT IN to get those free products.

In reality we should have stuck with 1090 only and never done the 978UAT. Then every one has traffic, since everyone else is 1090. The only reason for TIS-B is because the GA community fought tooth and nail for the right to fly without ADS-B. So to give everyone a more complete traffic picture the FAA invented TIS-B.

So while the rest for the world has a simple 1090 system. We ,being like typical Americans , have a frankensystem because everyone doesn't want to play together.
 
ARFlyer said:
US made it complicated by introducing two systems. The rest of the world uses 1090 and doesn't need all this In/ Out crap. FAA did 978UAT to throw a bone to GA to support the ATC upgrades. Then to force you to get the upgrade, they said you have to have UAT IN to get those free products.

In reality we should have stuck with 1090 only and never done the 978UAT. Then every one has traffic, since everyone else is 1090. The only reason for TIS-B is because the GA community fought tooth and nail for the right to fly without ADS-B. So to give everyone a more complete traffic picture the FAA invented TIS-B.

So while the rest for the world has a simple 1090 system. We ,being like typical Americans , have a frankensystem because everyone doesn't want to play together.
Click to expand...

Couldn't stick with only 1090. Under high traffic density there isn't enough airtime to handle all the transmissions necessary. That's pretty much the only reason we have 978, because the fancy new system wouldn't have worked reliably in the places it is needed the most.

Interesting that it's turning out not to be reliable in the places it's needed most with 978. They need to remove the "puck" filters and just send the traffic up by geographic location and tower coverage to make it a sanely engineered safety system. Right now, it's an over-engineered novelty system as likely to warn you as not. No point in paying $2B for the ground network at all, so far. Let alone the airborne costs.
 
denverpilot said:
Couldn't stick with only 1090. Under high traffic density there isn't enough airtime to handle all the transmissions necessary. That's pretty much the only reason we have 978, because the fancy new system wouldn't have worked reliably in the places it is needed the most.

Interesting that it's turning out not to be reliable in the places it's needed most with 978. They need to remove the "puck" filters and just send the traffic up by geographic location and tower coverage to make it a sanely engineered safety system. Right now, it's an over-engineered novelty system as likely to warn you as not. No point in paying $2B for the ground network at all, so far. Let alone the airborne costs.
Click to expand...

Well makes since. Can only pack so much data into a radio burst.

I agree on getting rid of the puck filters. It leads to traffic being shown then dropped, then shown, then dropped. I've watched TIS-B traffic bounce like this many times until your system and the FAA system makes up its mind.
 
You must log in or register to reply here.
Back
Top