Collision avoidance system

Claim 1

In a position-finding collision avoidance system at an Own station that passively derives differential azimuth (A), differential time of arrival (T), identity (ID) and altitude (H) data regarding transponder equipped Other stations utilizing standard ground ATCRBS interrogations and transponder replies thereto, and updates the positions of Own and Other stations for display at Own station, apparatus for initially establishing Own station's position, comprising: a. means for transmitting a brief burst of interrogations in standard ATCRBS format utilizing a signature and repetition rate substantially different from that of any SSR, b. means for receiving replies to said interrogations from all Other stations within range, c. means for selecting from said replies by the Other stations only those replies that are not garbled, d. means for determining the direct range Y from said Own station to one or more of said Other stations whose non-garbled replies correlate with the time intervals between said interrogations and the replies thereto, and e. means for computing the Own station's initial position from said one or more ranges Y, the known positions of the participating SSRs and the A, T, ID and H data derived from the standard ground ATCRBS interrogations from said SSRs and transponder replies thereto from said one or more Other stations.

Claim 16

The method of determining the distance D between two SSRs at an Own station within the common service area of said SSRs, said service area also encompassing a transponder-equipped Other station, including the steps of: a. transmitting interrogations from said Own station and receiving replies thereto from said Other station, b. determining the distance Y of said Other station from said Own station from the time delay between transmission of said interrogations and the reception of replies elicited thereby, c. deriving the differential azimuths (A) and the differential times of arrival (T) data regarding said Other station with reference to said SSRs, d. computing, from said data and said distance Y, the lengths of lines R1 and R2 from said Own station to said SSRs and the angle θ between said lines, and e. solving the triangle defined by said lines R1 and R2 and said angle θ for the side D opposite said angle θ.

Claim 17

The method of determining the distance D between two SSRs at an Own station within the common service area of said SSRs, said service area also encompassing a transponder-equipped Other station, including the steps of: a. transmitting interrogations from said Own station and receiving replies thereto from said Other station, b. determining the distance Y of said Other station from said Own station from the time delay between transmission of said interrogations and the reception of replies elicited thereby, c. deriving the differential azimuths (A) and the differential times of arrival (T) data regarding said Other station with reference to said SSRs, d. computing, from said data and said distance Y, the lengths of lines R1 and R2 from said Own station to said SSRs and the angle θ between said lines, and e. solving the triangle defined by said lines R1 and R2 and said angle θ for the side D opposite said angle θ.