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9

I'm convinced this numbers were fligtradar-internal identifiers, nothing concerning the flights themselves. The following is not an answer, just what I know about flightradar data records and where to find data like yours. The flightradar website on a computer updates its data by requesting this url, which contains coordinate bounds, filter settings and so ...


7

Aircraft equipped with Mode S transponders transmit a unique 24 bit aircraft ID, in addition to a 4 digit transponder code (squawk). There are two ways of displaying this unique ID, as an 8 digit xxdecimalxx octal number or as a hexadecimal value. Your examples are are hexadecimal values and translate as xxx23563319xxx and xxx23563320xxx 131706067 and ...


7

ADS-B, Automatic Dependent Surveillance - Broadcast, is a broadcast of the aircraft's position and other information. The position is determined by a GPS receiver. It is possible to use another qualified position source, but today it is de facto GPS. Other GNSS (Galileo, GLONASS, Bei-Dou) are other likely candidates in the future, but as far as I know, ...


6

Messages with Downlink Format 17 are, as you know, ADS-B messages that do not require interrogation. As such the interrogator ID will be zero. Frequently you will see that, after applying the CRC check, the CRC remainder is non-zero. This is caused by corruption of the ADS-B message between the transmitter (see note) and the receiver. This is partly ...


4

ADS-B IN systems do require information from the 0x6X registers. These registers hold information like ADS-B protocol version, system design assurance level and position source quality indicators. Without this information the ADS-B IN system can establish a track, but the quality will be flagged as too low to display. For reference, get a copy of RTCA DO-...


4

The two aircraft in question were actually only one. Apparently it was a glitch in the FR24 system. It was an Embraer ERJ-190AR, registration number N949UW on flight AA1678 from ATL to LGA. This also pretty much validates sweber's assertion that the numbers are internal FR24 codes, because the mode-S ID is AD306E.


3

ADS-B is more accurate. SSR calculates the distance to a target based on when it receives a reply from the transponder, which is inherently imprecise, and calculates the azimuth by the sweep, which is also inherently imprecise. A blip on a radar scope isn't exactly where the plane is but rather the center of an area where the plane is most likely to be. ...


2

In case of imminent danger remember these three words: aviate, navigate communicate. In that order. Aviate: make sure you keep flying the aircraft, and keep it flying in one piece. Navigate: know what is around you and control where you are going. Avoid crashing into anything or anyone else. Communicate: let ATC and/or other aircraft know what your ...


2

Mode S ADS-B messages use DF17 or DF18. The type code field with the DF17/DF18 is set to reflect the current navigation performance. The Containment Radius (Rc) is the radius that there is a 95% probability the aircraft is within that radius of its stated position, both horizontally and vertically. HPL is computed by the GNSS and is the theoretical ...


2

Your calculation of $this->_pi just ORs the three parity bytes together, which certainly doesn't make any sense. I'm not sure what you hope to get out of that. Even XORing them together wouldn't seem to serve any purpose. Addressing and checksumming in the Mode S protocol work in a funky way, in order to save bits. The last 3 bytes of a message are ...


2

According what I could find in Annex 10, DF-17 messages are always supposed to have zero interrogator IDs -- so if you get any of those that don't pass the parity check, they must have been garbled. On the other hand, DF-11 messages will often be sent with a nonzero interrogator ID. As specified, the interrogator ID after removing the CRC will always be ...


2

I think the problem is that you see a Mode 3/A (identity) reply, but you try to interpret it as Mode C (altitude reply). In Mode C, altitude is Gillham encoded, using all pulses except for D1 and X. This gives a range of -1200 to 126700 ft in 100 ft increments. If you see a D1 pulse, you are not looking at a Mode C reply. In Mode A, a 12 bit identity (...


1

ADS-B has two defined datalinks, 1090ES and UAT978. UAT978 is, so far, only available in the US. FIS-B is weather radar and similar data, and is only available on UAT978. 1090ES datalink is an enhancement to Mode S that adds DF17 messages with position, velocity and other ADS-B data. TIS-B is a ground-based service that transmits ADS-B-like messages on ...


1

All the recorded transmissions you have, seem to come from the same aircraft. They come all from the onboard (Mode-S) transponder. All transmission with Downlink Format (DF) 17 are ADS-B. Those with DF18 are TIS-B (or ADS-R), you don't have any of these (they are rare in Europe, and more common in the US) Mode-S uses the following DF's: DF4 - altitude ...


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