Method of altitude track initialization in an aircraft tracking system

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. The binary or coded altitude data of the non-adjacent and adjacent replies are further compared whether or not the replies have binary data of low or high confidence to determine whether an altitude track may be initialized. The process applies if the altitude data is Gilham code, binary, or other encoded data with single bit errors.

Dependencies are inferred from the claim text.