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66 votes

Why don't all commercial aircraft transmit GPS data in real time?

Most commercial aircraft transmit their GPS-based position twice per second. This is part of their Automatic Dependent Surveillance – Broadcast (ADS–B) broadcasts. The problem with providing world-...
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59 votes
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Why are commercial flights not (publicly) trackable in some locations?

The reason is that there is no member of the general public in those areas with an ADS-B receiver sharing live data with the public tracking sites. Websites like Flight Radar 24 rely largely on ...
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37 votes
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Why do aircraft on Flight Radar 24 jump around randomly sometimes?

FR24 relies for most of the tracks on ADS-B data. Part of the ADS-B transmissions is the position. There are three causes of the behaviour that you observe: 1). Aircraft landing next to the runway The ...
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34 votes
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What are these vehicles with no callsign used for?

They have Mode-S transponders / ADS-B transmitters specifically for vehicles such a the ERA SQUID, Thales MOSQUITO or Saab Sensis VeeLoPDF. Typically vehicles that operate on taxiways and runways ...
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26 votes
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Do pilots ever use the aircraft's ICAO 24-bit address when communicating with ATC?

Typically pilots do not know the 24-bit aircraft address of their aircraft. The 24 bit address is intended for data protocol level of communications and is not used in voice communication. Therefor ...
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21 votes

How does ATC radar/ADS-B ground stations not get confused with signals sent from multiple aircraft?

The class of ATC radars that you are talking about is secondary radar. Secondary radar works by transmitting an interrogation signal on 1030 MHz to which the transponder replies on 1090MHz. There ...
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20 votes
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How can ADS-B replace primary radar when FlightRadar24, using ADS-B, is so inaccurate?

TLDR How will ADS-B actually reliably replace primary radar? It will not. Will GPS have become mandatory by 2020? Strictly speaking no, effectively yes. There are so many problems with that quote ...
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19 votes

Why do aircraft on Flight Radar 24 jump around randomly sometimes?

Not to take away from already great answer provided. In my experience the jumping behavior you are describing in Flightradar24 is due to MLAT triangulation that is used to establish approximate ...
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19 votes

Why don't all commercial aircraft transmit GPS data in real time?

The following is, in respect of aircraft, speculation. However, I did spend a decade working on the GPS based tracking systems mentioned in the question, with particular emphasis on remote operations ...
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18 votes
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Why are there so many ADS-B ground towers in western Colorado?

As GdD commented, the cluster you noticed is not near Denver, but Montrose, CO. The reason for this cluster is Wide Area Multilateration (WAM) with ADS-B. This technique uses many sensors distributed ...
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15 votes

How can ADS-B be secure when it is based on self-reporting?

Yes, one can send deliberately wrong position reports. But why would anyone want to do that? We're assuming malicious intent, of course -- but even so? Could an attacker cause a collision using fake ...
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15 votes

What does prevent installing an ADS-B transponder on a vehicle?

Use of ADB-S transmitters is limited by regulation: in the US, frequency use is limited to FCC license holders; FCC licenses are delivered only after approval by FAA, the aviation agency; FAA approves ...
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14 votes
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Why did this aircraft re-route?

Its hard to tell from the picture, but assuming you are talking about the yellow airplane and the "wiggle" in the course, that was probably just an S-turn for spacing. Sometimes the controllers don't ...
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14 votes
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What is the relation between aircraft altitude and ADS-B coverage?

The ADS-B signal used by FR24 is transmitted on 1090 MHz. Signals at that frequency do not follow the curvature of the earth very well. They work best in line of sight. Aircraft far away from the ...
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14 votes
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Is ADS-B intended to replace other traffic management systems?

For a short introduction on what ADS-B is and why it is called dependent see this answer. ADS-B is a surveillance technology whereby the aircraft broadcasts information about its identity, position, ...
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13 votes
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How can I determine takeoff and landing from an ADS-B feed?

It depends on the type of ADS-B feed you have. On the lowest level, the messages transmitted from the aircraft, usually contain information about the air/ground status of the aircraft1. When the ...
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13 votes
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On an ADS-B In display, do the pilots see the squawk code or call sign for other aircraft?

ADS-B is part of a system that compromises a number of different things. ADS-B (In) means that your aircraft is capable of receiving the ADS-B data, FIS-B and TIS-B as well. FIS-B broadcasts ...
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12 votes

How does the ADS-B compact position report NL() function work?

Compact Position Reporting (CPR) is a way of reducing the number of bits needed to transmit position whilst maintaining high position resolution (~5.1 meters for airborne encoding). Ordinary encoding ...
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11 votes
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Why weren't SA-On GPS units updated to become SA-Aware?

As the linked ICAO article on GPS accuracy states, the issue is not just the navigation accuracy but the reported accuracy which is critical when used for ADS-B. From the report: 3.2.1 For GPS ...
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10 votes
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How can ADS-B be secure when it is based on self-reporting?

You aren't missing anything obvious, ADS-B spoofing (the sending of faked messages) and tampering (putting incorrect information into a message) is possible as there is no message authentication built ...
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10 votes

My N number showed up on another plane's flight on FlightRadar24. How does that happen?

FR24 may not actually receive any N-number from the aircraft. It's not unlikely that it only receives the Mode-S transponder code and cross-references that with a database to your N-number. So the ...
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9 votes

What kind of ADS-B identification code is FFxxxx, where xxxx are numbers i.e. FF0024?

I am going to assume you use Flightaware's variety of dump1090 as a decoder. When that receives a Mode A code, it publishes it as if it were a 24 bit address. The first two hexadecimal digits are ...
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9 votes
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What ICAO codes are reserved for TIS-B use?

In this answer I'll assume you are analysing ADS-B data on 1090 MHz, which is the defacto global standard. I am less familiar with the ADS-B on UAT (987 MHz) which is used in addition to 1090MHz in ...
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9 votes
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Does ADS-B signal contain the aircraft type?

No, the airplane type is not in the signal. The identification contains the ICAO 24bit (Mode S) code. You then need to map that to a registration which will have the type. As mentioned in the ...
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9 votes
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Can ATC provide vectors and separation service to and between IFR aircraft in areas where radar coverage does not exist using ADS-B only?

Yes. In the United States, ADS-B may be used as the sole surveillance source for the provision of ATC services (including IFR-IFR separation) provided that the automation system ("radar scope&...
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8 votes
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Is ADS-C used in practice?

ADS-C is used in oceanic environments, for example over the Atlantic and the Pacific. FL350 to FL390 on the North Atlantic Track System is restricted to ADS-C equipped aircraft. Non ADS-C aircraft ...
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8 votes
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How many commercial jetliners are equipped with ADS–B?

The majority of commercial airliners are currently equipped. I don't have the latest statistics, but for Europe over 80% of the airliners were equipped with 1090 Extended Squitter ADS-B two years ago. ...
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8 votes

What are these vehicles with no callsign used for?

On this question it is mentioned that ground support vehicles are equipped with ground transponders that work with the airport ground radar. I doubt they have ADS-B. They are most likely getting a ...
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