METHOD FOR LOCATING VEHICLES

• US 3,848,254 A
• Filed: 06/14/1972
• Issued: 11/12/1974
• Est. Priority Date: 07/28/1971
• Status: Expired due to Term

• Current Assignee: Klaus Drebinger, Peer Thilo
• Original Assignee: Klaus Drebinger, Peer Thilo
• Inventors: Drebinger, Klaus, Thilo, Peer
• Primary Examiner(s): Hubler, Malcolm F.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/262,626
• Time in Patent Office: 881 Days
• Field of Search: 343/112TC
• US Class Current: 342/457
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence

Abstract

A method for locating surface vehicles, particularly in a city area, in which the vehicle to be located transmits a measuring radio signal which is received by at least three differently located radio receiving stations, with the signal values received at each station being conducted, in suitable form, over fixed lines to a central station at which the transit time differences of the measuring signal on its path towards two different receiving stations are determined by means of a phase comparison, with transit time fluctuations occurring in the receiving and transmission devices being compensated by additionally obtained correction values, for example, derived from signals received by the respective receiving stations from a fixed location with known distances from such receiving stations, and evaluating at least two such independent difference values for the determination of the location of the vehicle.

Claims

1. A method for locating surface vehicles, particularly in a city area, in which the vehicle to be located transmits a measuring radio signal which is received by a plurality of differently located radio receiving stations, comprising the steps of transmitting from such vehicle, for each location operation, a plurality of measuring signals of relatively low frequency, modulated on a relatively high frequency carrier, receiving such measuring signals by a plurality of receiving stations, greater in number than the minimum number required to define a location, demodulating the received signals in the respective receiving stations, conducting the demodulated signals over respective fixed, corresponding low frequency lines to a central station, deriving correction values by similarly transmitting like measuring signals from a fixed location with known distances to the respective receiving stations, transmitting the corresponding demodulated low frequency signals from the respective receiving stations to the central station, utilizing thereat corrections derived therEfrom to effect corrections in transmission of the corresponding demodulated signals between the central and receiving stations, utilizing the average of a plurality of received corresponding low frequency signals from the respective receiving stations to determine, in the central station by means of a phase comparison, respective transit time differences of the measuring signal on its path towards respective different pairs of receiving stations, and effecting an electronic computation to drive a location-defining point by hyperbolic intersection, thereby determining the location of the vehicle.

2. A method according to claim 1, comprising the step of initiating transmission of a measuring signal from the vehicle transmitter by transmission of a command signal from the central station.

3. A method according to claim 2 wherein the command signal employs a multi-frequency code whereby it is operatively received by only a selected vehicle.

4. A method according to claim 2 wherein the command signal is time-multiplexed whereby it is operatively received by only a selected vehicle.

5. A method according to claim 2 wherein the command signal is simultaneously transmitted to a group of vehicles and the vehicles of such group transmit their respective measuring signals in a fixed succession by means of a cyclic interrogation.

6. A method according to claim 1, wherein each vehicle transmits an identification signal simultaneously with the measuring signal.

7. A method according to claim 1, wherein additional information is transmitted by means of further signals, with or separate from the measuring signal.

8. A method according to claim 1, wherein broad band limiting is employed to reduce transit time distortions due to level fluctuations at the receiving stations.

9. A method according to claim 1, wherein a constant intermediate frequency is formed at the high frequency receivers of the receiving stations, and controlling the local mixing frequency in the presence of frequency deviations in the transmission from a vehicle.

10. A method according to claim 1, comprising the step of excluding from evaluation measuring signals which involve interference distortions.

11. A method according to claim 1 wherein corresponding measuring values are relatively far apart and not taken into account in the formation of an average value.

12. A method according to claim 1, wherein the respective shortest transit times from several successively received measuring signals, are derived from a comparison with a central time basis and utilized for the location determination.

13. A method according to claim 1, comprising the steps of comparing each determined location of a vehicle with the preceding location determination thereof and taking the same into account only when the distance of the two measuring points are consistent with the maximum driving speed of the vehicle.

14. A method according to claim 1, wherein the evaluation of measuring signals is effected only with vehicles which have changed their positions.

15. A method according to claim 14, wherein a differentiation between stationary and moved vehicles is effected by a comparison of the fluctuation magnitude and fluctuation frequencies of the values obtained during a measurement.

16. A method according to claim 14, wherein stationary vehicles are indicated by a particular signal transmitted with the measuring signal.

17. A method according to claim 14, wherein a transmission of a measuring signal from a vehicle is effected only during movement of the vehicle.

18. A method according to claim 1, wherein directional reception is utilized at the receiving stations.

19. A method according to claim 1, comprising the step of reproducing the individual vehicle location on a television monitor.

20. A method according to claim 1, comprising the step of representing the individual vehicle locations by projecting respective identifying light dots on a picture surface.

21. A method accordiNg to claim 18, comprising representing the individual vehicles by light dots of different colors.

22. A method according to claim 19, comprising representing the individual vehicles by light dots of different colors.