Originally Posted by
SpringHeeledJack
Maybe they turn off M-LAT or whatever under a certain altitude for their own reasons, whatever they may be ?
Multilateration is progressively more difficult to achieve as altitude decreases, as it depends on the aircraft's transmissions being received simultaneously by several different ground stations, and that requires line-of-sight from each of them.
Originally Posted by
jmmoric
One of the most insecure systems ever invented.....
Are you talking about MLat? Or ADS-B/Mode S in general ?