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. ...
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 ...
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 (...
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 ...
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 ...