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A location system and method whereby the azimuth and range information of an aircraft with respect to a reference ground station is made available to other aircraft by transmission of a pulse at a time uniquely associated with the aircraft's location. A synthetic azimuth function and a synthetic ran

A location system and method whereby the azimuth and range information of an aircraft with respect to a reference ground station is made available to other aircraft by transmission of a pulse at a time uniquely associated with the aircraft's location. A synthetic azimuth function and a synthetic range function provide a periodic mapping of an area. The synthetic azimuth function is a slowed, time-expanded representation of a conventional azimuth function. Each azimuth increment is allocated a time slot in the synthetic azimuth function. The synthetic azimuth function is synchronized by counting a number of synchronizing pulses from the conventional azimuth function, and a synthetic azimuth reference pulse is periodically transmitted from a reference ground station to synchronize all aircraft using the synthetic azimuth function. During the particular synthetic azimuth function time slot corresponding to an aircraft's azimuth, a pulse is transmitted and the aircraft's range is encoded as the time-delay of that pulse with respect to the most recent conventional azimuth synchronizing pulse, providing a synthetic range function which is embedded in one of the synthetic azimuth degree increments. Display and collision warning devices are also synchronized and operated by this location system.

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1. A system enabling a parent aircraft to determine the location of a target aircraft, comprising: first means aboard a parent aircraft and a target aircraft, each for generating a synthetic azimuth function which is a time-expanded version of a periodic azimuth function describing the aircraft's

1. A system enabling a parent aircraft to determine the location of a target aircraft, comprising: first means aboard a parent aircraft and a target aircraft, each for generating a synthetic azimuth function which is a time-expanded version of a periodic azimuth function describing the aircraft's azimuth as a time-delay with respect to the occurrence of an azimuth reference signal; second means aboard the parent aircraft and target aircraft, each for generating a time expanded synthetic range function, which function describes the aircraft's range as a time-delay with respect to the occurrence of a range reference signal; means for providing the target aircraft with a signal representative of its azimuth with respect to a reference position and for providing the target aircraft with a signal representative of its range with respect to the reference position; transmitter means aboard the target aircraft for transmitting an output signal at a time when the target aircraft's representative azimuth and range signals correspond, respectively, to the synthetic azimuth and synthetic range functions; and means aboard the parent aircraft for comparing the transmitted output signal from the target aircraft to the synthetic azimuth function and to the synthetic range function generated by the first and second means aboard the parent aircraft and providing an output signal to the operator of the parent aircraft indicative of the location of the target aircraft. 2. The system of claim 1, wherein the comparing means aboard the parent aircraft includes computer means. 3. The system of claim 2, wherein a visual display system is provided aboard the parent aircraft which is synchronized by a series of periodically repeating signals derived from a conventional system synchronizing signal, this synchronizing signal also synchronizing the synthetic azimuth function and the synthetic range function and which provides a visual display of the location of the target aircraft. 4. The system of claim 1, wherein the synthetic azimuth function has a period which is a multiple of the period of the azimuth function. 5. The system of claim 1, wherein the transmitter means includes means for encoding the target aircraft's altitude in the transmitted output signal and wherein the parent aircraft contains means for enabling the comparator means when a preset altitude code is received. 6. The system of claim 1, including alarm means on board the parent aircraft which is actuated in response to receipt of a transmitted output signal indicative of the target aircraft being within a predetermined distance from the parent aircraft. 7. The system of claim 1, including means for correcting for the time delays due to the time required for radio frequency energy to travel over finite distances. 8. An aircraft location system which utilizes conventional position determining equipment providing output signals having azimuth and range information with respect to a fixed reference location, said conventional position determining equipment also providing a periodic azimuth synchronization signal, comprising: first means for generating a synthetic azimuth function, which function is a time-expanded version of a conventional periodic azimuth function, said generating means including means for generating a periodic synthetic azimuth synchronization signal from the periodic azimuth synchronization signal, said synthetic azimuth function describing an aircraft's azimuth as a time delay with respect to the occurrence of the periodic synthetic azimuth synchronization signal, said first generating means providing an output signal representative of the synthetic azimuth function; second means for generating a synthetic range function which describes an aircraft's range as a time delay with respect to the occurrence of one of the conventional periodic azimuth reference signals, said second generating means providing an output signal representative of the synthetic range function; means for encoding an aircraft's position in terms of the synthetic azimuth function and in terms of the synthetic range function, said encoding means providing an output signal at a time, measured from the periodic synthetic azimuth synchronization signal, corresponding to the aircraft's position; comparator means for comparing the synthetic azimuth function signal to the encoded aircraft azimuth output signal and for comparing the synthetic range function signal to the encoded aircraft range output signal, said comparator providing and output signal indicative of the coincidence of the respective signals being compared so that the location of an aircraft in terms of the synthetic azimuth function and the synthetic range function is obtained. 9. The system of claim 8, including transmitting means responsive to the comparator means output signal. 10. The system of claim 8, wherein the signals compared by the comparator means are encoded digital signals. 11. The system of claim 10, wherein the comparator means includes computer means. 12. A location system for an aircraft, comprising: a transmitter at a fixed location providing a periodically pulsed synthetic azimuth reference synchronizing signal and also providing a periodically pulsed synthetic range reference synchronizing signal having a period which is a sub-multiple of the period of the synthetic azimuth reference synchronizing signal, said synthetic range reference synchronizing signals providing equal synthetic azimuth degree increments; means for providing the azimuth and range information of the aircraft with respect to the transmitter location; means for encoding the azimuth of the aircraft with respect to the transmitter location as a synthetic azimuth pulse having a time delay with respect to the synthetic azimuth reference synchronizing signal, which time delay is proportional to the azimuth of the aircraft with respect to the transmitter location; means for encoding the range of the aircraft as a synthetic range pulse having a time delay with respect to the synthetic range reference synchronizing signal, which time delay is proportional to the range of the aircraft from the transmitter location; means for transmitting an aircraft location signal at a time corresponding to the simultaneous occurrence of the synthetic azimuth pulse and the synthetic range pulse; means for receiving said aircraft location signal and for decoding the azimuth information and the range information to obtain the position of the aircraft with respect to the transmitter at the fixed location; and means for displaying the position of the aircraft relative to the transmitter location. 13. The system of claim 12, wherein the means for transmitting the aircraft location signal is on a first aircraft and the receiving and decoding and display means are on a second aircraft so that the first aircraft's position is provided to the second aircraft. 14. The system of claim 13, wherein the second aircraft includes means providing azimuth and range information of the second aircraft with respect to the reference transmitting means, and includes means for displaying the position of the second aircraft relative to the transmitter at the fixed location. 15. The system of claim 14, including means for computing the distance between the first and the second aircraft and means for indicating that said aircraft are within a predetermined distance of each other. 16. The system of claim 15, including means for correcting for the time delays due to the time required for radio frequency energy to travel over finite distances. 17. A method for providing information about the location of an aircraft, comprising the steps of: generating a first synthetic function which is a transformed version of a first conventional function and which describes one coordinate of the aircraft's position; synchronizing the first synthetic function with a first synchronizing pulse derived from signals from the first conventional function; generating a second synthetic function which describes another coordinate of the aircraft's position; synchronously starting and stopping the second synthetic function within the time required for a predetermined degree change in the first synthetic function by synchronizing the second synthetic function with pulses which are derived from signals from the first conventional function; and transmitting a pulse at a time when the value of the first synthetic function and the second synthetic function corresponds to the coordinates of the aircraft's position. 18. The method of claim 17, wherein the first synthetic function is a linear transformation of the first conventional function. 19. The method of claim 18, including generating the first synthetic function as a time-expanded azimuth function with respect to a reference point and including generating the second synthetic function as a range function with respect to the reference point. 20. The method of claim 19, including synchronizing the first synthetic function by generating a synthetic azimuth synchronizing signal derived from the first conventional function. 21. A method of air collision avoidance, comprising the steps of: time encoding azimuth information by generating a synthetic azimuth function which expands the time period for a conventional azimuth function from 1/30th of a second to a greater number of seconds, azimuth information being encoded as a time delay with respect to a synthetic reference azimuth synchronizing pulse which occurs once for every 360 conventional azimuth synchronizing pulses; encoding range information by generating a synthetic range function which makes range information proportionate to a time delay with respect to the most recently occurring azimuth synchronizing pulse; and transmitting a signal from an aircraft, the time of which signal, measured from the occurrence of the synchronizing pulses of the synthetic azimuth and range functions, respectively, is indicative of the aircraft's position in terms of the synthetic azimuth and range functions. 22. A method for expanding the azimuth resolution of a conventional polar-scanned vehicle position determining system which transmits a periodic signal reference, comprising the steps of: generating a synthetic azimuth scan function having an angular scan rate which is a sub-multiple of the conventional polar-scanned system angular scan rate; and encoding range information by making range information proportional to the start of the conventional polar-scanned system angular reference position signal, which is used to produce a range synchronizing signal. 23. A method for enabling a parent aircraft to determine the location of a target aircraft, comprising the steps of: generating a synthetic azimuth function, which function is a time-expanded version of a periodic azimuth function describing an aircraft's azimuth as a time-delay with respect to the occurrence of an azimuth synchronizing signal; generating a synthetic range function, which function describes an aircraft's range as a time-delay with respect to the occurrence of a range synchronizing signal; providing the target aircraft with a signal representative of its azimuth with respect to a reference location and providing the target aircraft with a signal representative of its range with respect to the reference location; transmitting an output signal at a time when the target aircraft's representative azimuth and range signals correspond to the synthetic azimuth and synthetic range functions, respectively; and comparing the transmitted output signal to the synthetic azimuth function and to the synthetic range function to provide an output signal indicative of the location of the target aircraft. 24. The method of claim 23, wherein the comparison step includes making the comparison by means of a computer. 25. The method of claim 23, including the step of providing a visual display system which is synchronized by the synthetic azimuth function and the synthetic range function to provide a visual display of the location of the target aircraft. 26. The method of claim 23, wherein the step of generating the synthetic azimuth function includes providing the synthetic azimuth function with a period which is a sub-multiple of the period of the azimuth function. 27. The method of claim 23, including the steps of encoding the target aircraft's altitude in the transmitter output signal and the step of enabling the comparator means when one of a preset range of altitude codes is received. 28. The method of claim 23, including actuating an alarm on board the parent aircraft in response to receipt of a transmitted output signal indicative of the target aircraft's being within a predetermined distance from the parent aircraft. 29. A method for providing the location of an aircraft, comprising the steps of: providing a transmitter at a fixed location which transmits a periodically pulsed synthetic azimuth reference synchronizing signal; providing a periodically pulsed synthetic range reference synchronizing signal having a period which is an integer submultiple of the period of the synthetic azimuth reference synchronizing signal to provide equal synthetic azimuth degree increments; providing azimuth and range information of the aircraft with respect to the transmitter location; encoding the azimuth of the aircraft with respect to the transmitter location as a synthetic azimuth pulse having a time delay with respect to the synthetic azimuth reference synchronizing signal so that the time delay is proportional to the azimuth of the aircraft; encoding the range of the aircraft as a synthetic range pulse having a time delay with respect to one of the synchronizing range reference synchronizing signals so that the time delay is proportional to the range of the aircraft from the transmitter location; transmitting an aircraft location signal at a time corresponding to the simultaneous occurrence of the synthetic azimuth pulse and the synthetic range pulse; receiving the aircraft location signal and decoding the azimuth information and the range information to obtain the position of the aircraft with respect to the transmitter at the fixed location; and displaying the position of the aircraft. 30. The method of claim 29, including the steps of transmitting the aircraft location signal from a first aircraft and the steps of receiving, decoding and displaying on a second aircraft so that the first aircraft's position is provided to the second aircraft. 31. The method of claim 30, including the step of providing azimuth and range information for the second aircraft with respect to the reference transmitter and including the step of displaying the position of the second aircraft relative to the transmitter. 32. The method of claim 31, including the step of computing the difference between the first and second aircrafts and indicating that said vehicles are within a predetermined distance from each other. 33. The method of claim 32, including the step of correcting for the time delays due to the time required for radio frequency energy to travel over finite distances.