Curious: what inputs feed your system? Presumably at least localizer and GPS, but anything else? What accuracy / confidence interval do you require in order to make a call?
We actually don't use the localizer to check for an incorrect runway or taxiway landing because the pilot can choose to do so and we don't want to issue nuisance alerts. Runways don't move often and we've found that a GPS and two databases (runways and airport ground features) are sufficient to determine if the pilot is approaching a runway or not.
We use inputs like GPS position, ground track, ground speed, altitude, and a phase-of-flight state machine that's determined for individual aircraft. This allows us to tailor the criteria for determining if the aircraft is landing for different aircraft. For some, we use throttle and landing gear position and others we use speed and altitude above the landing airport.
As for accuracy, we have minimum levels of GPS figure of merit where there's enough certainty to issue alerts. I don't remember the number off the top of my head, but in the US WAAS has made GPS quite accurate.
We use inputs like GPS position, ground track, ground speed, altitude, and a phase-of-flight state machine that's determined for individual aircraft. This allows us to tailor the criteria for determining if the aircraft is landing for different aircraft. For some, we use throttle and landing gear position and others we use speed and altitude above the landing airport.
As for accuracy, we have minimum levels of GPS figure of merit where there's enough certainty to issue alerts. I don't remember the number off the top of my head, but in the US WAAS has made GPS quite accurate.