Abstract: A method of processing a plurality of replies of target aircraft provided in response to interrogation signals from the surveillance aircraft during surveillance periods to determine whether an altitude track may be initialized for use in a traffic alert and collision avoidance system includes the step of selecting three replies, one from each of three consecutive surveillance periods. The replies have binary or coded altitude data of high or low confidence. The binary or coded altitude data of non-adjacent and adjacent replies of the selected replies are compared and an altitude difference value for each of the comparisons is generated. Further efforts to initialize a track are discarded if any of the altitude difference values are greater than first predetermined separated altitudes if and only if such compared non-adjacent and adjacent replies have binary or coded altitude data of high confidence.

Abstract: In a Traffic Alert and Collision Avoidance System (TCAS), response to interrogations can result in normal, multipath (image), and mixed multipath (potential image) tracks. The method for reducing the number of false tracks includes the steps of selecting a track to be updated from an existing track list. The selected track has the shortest measured range within the highest priority category track. A reply which has not yet been utilized is selected which has parameters which are within predetermined windows of the selected track parameters. (The predetermined windows are equal to or smaller than the windows for lower priority targets.) The selected track is updated using .alpha..beta..gamma. range squared filter, and the selected reply is marked as used. After all tracks are updated, the unused replies are tested to generate new tracks. Then all the tracks are examined to insure that predetermined track category criteria are met, otherwise the track is recategorized.

Abstract: A system wherein TCAS transmissions have two jitter components added to the jitter component utilized in the interscan interval to minimize TCAS interference with ground station operation. The jitter components minimize the establishment of false intruder tracks caused by responses to ground station interrogations or interrogations by other TCAS interrogators which are received in synchronism with the TCAS interrogation signals.