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  #1  
Old 11-08-2013, 10:56 AM
JoeLofton JoeLofton is offline
 
Join Date: Jul 2006
Posts: 145
Default ADS-B Traffic System Report

I just completed a 2500nm round trip (spread over 2weeks) after installing an ADS-B system in my RV-3 (Garmin 796 GPS, Garmin GDL-39 ADS-B receiver, Trig TT-21 Mode S transponder). Observations on the traffic side of the system:

1) The system was accurate. The targets that I was able to see were where the system reported them.

2) There were lots more aircraft in relatively near proximity than I expected. I passed within a couple miles of several that I could not locate visually. Hardest to spot were those below that tended to get lost in the ground clutter. An aircraft a mile or two away is a small visual target. I'm sure my little airplane is even harder to spot.

3) The system added a layer of safety. Twice I jogged off track a couple of miles to give space to an aircraft that appeared to be converging at my altitude.

4) Of course the highest density of traffic was around airports. The system helped me keep track of other planes approaching airports where I was landing.

5) Still have to keep the eyeballs outside the cockpit most of the time - the system doesn't show birds, for instance. And, flying low because of headwinds, I came upon a couple of towers in the middle of nowhere in northern MS that reached almost 2500ft AGL - truly scary things.

I was pleased with the system - good to have more info in the cockpit. The weather side worked well also, once at enough altitude to see a ground station.

Joe Lofton
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  #2  
Old 11-08-2013, 11:22 AM
molson309 molson309 is offline
 
Join Date: Jul 2009
Location: Longmont, CO
Posts: 249
Default

Nice report.

I have ADS-B in my Rocket and around MSP it is great. When flying to Oshkosh, though, I found the reported traffic to not be in the place the system said it was, mostly in position but at least once in altitude. This was in the Ripon area and also to the northwest of it. Very perplexing. This happened to me 2 years in a row. Perhaps the targets were far enough from the radar site that position was subject to a large error margin, though I'd think the altitude would always be close.

So while it's nice, don't count on the reported traffic to always be where it is displayed.
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  #3  
Old 11-08-2013, 12:00 PM
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Brantel Brantel is offline
 
Join Date: Mar 2006
Location: Newport, TN
Posts: 7,509
Default

Quote:
Originally Posted by molson309 View Post
I found the reported traffic to not be in the place the system said it was, mostly in position but at least once in altitude. This was in the Ripon area and also to the northwest of it. Very perplexing. This happened to me 2 years in a row. Perhaps the targets were far enough from the radar site that position was subject to a large error margin, though I'd think the altitude would always be close.

So while it's nice, don't count on the reported traffic to always be where it is displayed.
This may be because when flying into Osh during the show, xponders are suppose to be set to standby in that area. Primary radar targets can move a great deal in relation to you between sweeps and the latency built into the uplink.

Altitude of Mode-C targets are only as accurate as the altimeter/encoder/static system install. Static position errors here can be significant and can go unnoticed during the typical xponder/alt/static checks.

We also know that non-certified position sources are being used by many at this time to feed position/velocity data to aircraft with ADS-B out. These sources may or may not be accurate.

As a whole, I have found the TIS-B uplink service and air to air ADS-B accuracy to be amazing. As always....Trust but verify with eyeballs on the target!
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Last edited by Brantel : 11-08-2013 at 12:04 PM.
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  #4  
Old 11-30-2013, 08:26 PM
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Nitty Nitty is offline
 
Join Date: Jan 2005
Location: Yuma Az
Posts: 119
Default Me and my ADS-B shadow

Just bought a skyradar d2 and was flying in Tuscon / Phoenix area when I saw a return right below me at nearly the same altitude. I turned and climbed and it followed me. I soon figured out that it was representing my aircraft. I don't have an ADS-B transmitter though so it's not getting my position data from me. My guess is that ATC is feeding position data but I didn't think it could do or is supposed to work that way.


From the image, my position is the blue aircraft at the bottom center. Underneath that symbol is my aircraft position shown by ADS-B.

Anybody else seen this?
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Last edited by Nitty : 11-30-2013 at 09:00 PM.
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  #5  
Old 11-30-2013, 09:24 PM
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Thermos Thermos is offline
 
Join Date: Jan 2005
Location: KASH
Posts: 543
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Quote:
Originally Posted by Brantel View Post
Primary radar targets can move a great deal in relation to you between sweeps and the latency built into the uplink.
TIS-B shouldn't be broadcasting tracks from primary-only targets.

Quote:
Originally Posted by Nitty View Post
My guess is that ATC is feeding position data but I didn't think it could do or is supposed to work that way.
In all likelihood an aircraft in your vicinity was broadcasting ADS-B Out, triggering the system to transmit TIS-B tracks. Since you probably had your Mode C transponder on, a secondary radar on the ground saw you and put your track into TIS-B - that's how you saw yourself on the iPad.

Dave S
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Last edited by Thermos : 11-30-2013 at 09:27 PM.
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  #6  
Old 11-30-2013, 09:41 PM
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billnaz billnaz is offline
 
Join Date: Jan 2005
Posts: 232
Default encoder alt

I too was freaked out by the traffic 100 feet directly underneath me which poped up itermittently. I figured out that it showed up when my foreflight altitude differed from my encoder alt. by more than a little. I dont have adsb-out, so I'm just getting shared data. Overall, I'd still rate the benefit as outweighing the imperfections of the system. It's amazing the traffic out there that would have gone unseen without it.
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  #7  
Old 11-30-2013, 11:03 PM
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Bill_H Bill_H is offline
 
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Location: Marshall TX (KASL)
Posts: 1,787
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Have Skyview with ADSB in and out. The ADSB weather radar imagary is cool - but I don't fly into that stuff, just around. What turns out to be REALLY cool for marginal VFR days is so easily calling up the current weather at airports on and off your route. Helps figure the best path very easily on the Skyview. Had similar positive experiences with the traffic - really helped me spot planes lower than myself, seeing overtaking traffic (would NEVER spot that visually) and in a couple of cases making an adjustment based on intersecting tracks. HUGE safety improvement.

Bill H. N412BR "Sweetie" RV12 Skyview 80 hours flying.
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  #8  
Old 12-01-2013, 06:13 AM
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Brantel Brantel is offline
 
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Location: Newport, TN
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Quote:
Originally Posted by Thermos View Post
TIS-B shouldn't be broadcasting tracks from primary-only targets.

Dave S
I have not seen anything officially saying they will or won't. I have seen targets that I was pretty sure were primary targets however. One day I saw a powered power chute.

I have also spotted a few aircraft visually that did not show up so who knows....
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Brantel (Brian Chesteen),
Check out my RV-10 builder's BLOG
RV-10, #41942, N?????, Project Sold
---------------------------------------------------------------------
RV-7/TU, #72823, N159SB
Lyc. O-360 carbed, HARTZELL BA CS Prop, Dual P-MAGs, Dual Garmin G3X Touch
Track N159SB (KK4LIF)
Like EAA Chapter 1494 on Facebook
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  #9  
Old 12-01-2013, 06:39 AM
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Rhino889 Rhino889 is offline
 
Join Date: Dec 2009
Location: Jupiter FL.
Posts: 451
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Quote:
Originally Posted by Nitty View Post
Just bought a skyradar d2 and was flying in Tuscon / Phoenix area when I saw a return right below me at nearly the same altitude. I turned and climbed and it followed me. I soon figured out that it was representing my aircraft. I don't have an ADS-B transmitter though so it's not getting my position data from me. My guess is that ATC is feeding position data but I didn't think it could do or is supposed to work that way.


From the image, my position is the blue aircraft at the bottom center. Underneath that symbol is my aircraft position shown by ADS-B.

Anybody else seen this?
My skyview has traffic alerted me several times at the bottom of a loop or Cuban. Gets your attention for sure. Adsb is a huge safety feature flying north/south along the Florida coast (human guided propeller cruise missiles). I also use my 8 to commute to Orlando international. It's an amazing enhancement to situational awareness.
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  #10  
Old 12-05-2013, 09:52 PM
Echo Tango Echo Tango is offline
 
Join Date: Nov 2009
Location: SFO Approach
Posts: 204
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Hey, can one of you guys stop by the radar room and drop one of these things off?
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