On Thursday, October 10, 2019 at 10:35:56 AM UTC-7, Dan Marotta wrote:
Can you get info on the targets?

In my Stemme and C-180 I have many different displays.Â* I can usually
get information which includes ICAO code (least informative), airline
flight number (not military), and N-number (also not military).Â* By
simple elimination one might assume the ICAO only code might be
military.Â* But you know about ass-u-me...

On 10/10/2019 10:58 AM, Eric Greenwell wrote:
Darryl Ramm wrote on 10/9/2019 12:26 PM:
Â* I'll try to do some counting of Southwest traffic stats on my ADS-B
receiver in the Bay Area.

My Phoenix has a Dynon Skyview EFIS with ADS-B in/out. Is there anyway
to tell the target is a military aircraft? Same question for the
Powerflarm in my ASH 26 E - can I determine a target is a military
aircraft (I have the simple rectangular display that just shows little
triangles)?


--
Dan, 5J

It's good to assume assuming is not always good. :-)

The formal identification data available via ADS-B (either UAT or 109ES) is

ICAO ID
Ident Characters (8 characters): The Flight Number or N-Number (targets don't transmit both).

You can also see any assigned squawk code and if the ident button has been recently pressed.

The ICAO ID can be super telling *if* you have access to the correct registration and/ or past observation databases, meaning typically on the ground connected to a computer. Just knowing if the ICAO address fits within a military reserved block may tell you if this is a military aircraft. That's the primary technique used to identify military traffic in this intersting paper on Military and State aircraft ADS-B traffic: https://opensky-network.org/files/pu...ons/dasc17.pdf In Europe disabling ADS-B Out for those aircraft has been a hot-topic of discussion.

There is a lot of other *potentially* telling information broadcast via ADS-B, e.g."emitter category" (e.g. heavy aircraft based in MTOW, light aircraft, sailplane, ... while nothing there says "military" directly the emitter category being say UAV or Highly Maneuverable ( 5 G and 400 TAS) could clue you in in some cases, wingspan and length (transmitted only on the ground), If it is 1090ES In or UAT In equipped, if it has TCAS, you can possibly tell something about how sophisticated it's avionics etc. e.g. wether transmitting GPS referenced velocity or/or air-referenced velocity, GPS altitude as well as pressure altitude, track data, etc. things there could make it possible to guess the level of sophistication and/or build up additional signatures to identify aircraft types.

Many airborne/end-user traffic systems don't display all this information, but it's all visible in open data to folks with the right tools, and/or a little programming skills--I modified dump1090 for example to gives me anything I want. I was going to show off some of that data, including watching some live ADS-R and TIS-B traffic processing, at the upcoming PASCO seminar.... but the seminar location has maybe the worst ADS-B tower ground coverage in SF Bay Area :-(

There can also be some extra data transmitted via Mode-S *without* ADS-B being involved that could also help give data on sophistication/capabilities of the aircraft. A TT21/22 in a glider can't do this, but sophisticated Mode-S transponder systems, (*independent* of ADS-B Out) can potentially transmit heading, track, roll rate, ground speed, airspeed, or FMS altitude select. etc. All possibly more fingerprinting clues.

I have a lot of empathy for the military operators here, ADS-B is a very surprising system, implemented with no fundamental encryption/authentication/security mechanisms. That's part of the publicly documented military concerns, it must be very strange for those military folks living in a modern IFF (Identification Friend or Foe) world, many of who recently upgraded to Mode 5 and are dealing with secure Mode 5 key provisioning etc. and then see this ball of unsecure/unauthenticated/wide open tangled string the FAA expects them to adopt.