In particular, to the extent that there are mandates for it in USA and Europe?
I checked various posts here and official descriptions (e.g., faa.gov), but I can't figure out the following:
- For continental (non-oceanic) usage, what benefits does ADS(-B) provide to ATC that is not possible with Mode S SSR?
I came to a dead end at How can ADS-B replace primary radar when FlightRadar24, using ADS-B, is so inaccurate? In particular:
ADS-B can and will replace a number of secondary radars, but not all of them.
By not all of them, I reckon those in congested areas will not be replaced, say the New York/New Jersey/Philadelphia Airspace. One could say to provide cheap coverage elsewhere where radars can't reach (too low targets), or not enough traffic to sustain the cost, but then for the FAA mandate, for example, outside Class A, B, C, and E (above 10,000 ft), one is not required to have ADS-B. (What is ADS-B and who needs it?)
I understand that there are plenty of beneficial uses for ADS: [Cheap] online tracking that benefits the operators and general public alike, and situational awareness for any GA pilot willing to spend money on ADS-B IN. But my question is about the benefits to ATC, that Mode S can't provide.
Edit: I found one usage (benefit?) in the post Is ADS-B intended to replace other traffic management systems?:
A more advanced usage of ADS-B will be flight deck based interval management (FIM) where ATC will be able to instruct aircraft to 'follow that plane XX seconds behind for landing on runway YY'.
Technologically, this is cool. But why the complication? Terminal airspace design that utilizes RNP routes, combined with requested times of arrival relayed to each aircraft, can accomplish the same, and is already a thing. Why let the separation be the responsibility of many, versus a few, i.e., bigger chance of something going wrong.
I'm thinking there must be more to it, even if not yet implemented.