Coordinate locating method and system

• US 3,886,553 A
• Filed: 03/15/1973
• Issued: 05/27/1975
• Est. Priority Date: 03/15/1973
• Status: Expired due to Term

• Current Assignee: Auretina Patent Management Corporation
• Original Assignee: John K. Bates
• Inventors: Bates, John K.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/341,729
• Time in Patent Office: 803 Days
• Field of Search: 343/112R,112TC 340/6R 235/150.272
• US Class Current: 342/465
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 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
• CPC Class Codes: Y10S 367/907 Coordinate determination

Abstract

A method and system are disclosed for measuring the geographical position of emitters such as radio transmitters accurately, simply, and inexpensively. In a particular application, the radio transmitters, which emit pulse type signals, may be located on small boats, for use in case of trouble, or on emergency vehicles. Widely spaced trilateration receiver stations are positioned to cover a preselected area and to receive the emitted signals. The relative time of arrival of each individual signal pulse at the several receiver stations is digitized and transmitted by way of communication channels to a central processing unit. At the central unit the time of arrival pattern of the pulses from the several receivers is compared with a pattern recognition matrix of previously mapped data. The central unit, being capable of responding only to preselected signal patterns, eliminates signals which originate outside of the preselected field of view and produces emitter location coordinants in digital numbers. The pattern recognition matrix is in the form of a logic array arranged to represent predetermined, discrete time delay increments as reference points in the geographical space under observation. The logic array produces coarsely quantized timevariable signal outputs. These time-variable output signals are interpolated in an array of variable-gain weighting devices using a centroid computing technique to finely locate the geographical coordinates of the transmitter. The system and method described have application to locating positions both in geographic as well as in geometric coordinate space. In the latter, the time of arrival pulse patterns are derived from time encoded analogs of physical measurements from various sensors where the measured parameters have a continuous functional relationship. There is stored in the matrix relatively coarse reference data containing the functional pattern. The input data, being continuous or finely quantized, is applied to the matrix. By virtue of the interpolation array, a smooth measuring of the position of the sample in the functional space is produced. This position is then interpreted by the user of the system. Stated in another manner, the method of this invention enables the use of prestored functional information to give the equivalent result of having stored a large amount of reference data.

Claims

1. A system for locating a point constituting an emitter in a continuous functional space defined by at least a pair of parameters comprising, in combination, sensor means for receiving manifestations from said emitter, means for encoding said manifestations in terms of relative time delay differences between the manifestations derived from differEnt ones of said sensor means, and comparator means for comparing the time of arrival pattern of said manifestations with a catalog of stored manifestations corresponding to predetermined sets of relative time difference patterns of said manifestations corresponding to different reference points in said space and providing a discrete output manifestation corresponding to the coarse location of said point in terms of said reference points.

2. A system according to claim 1 wherein said comparator means is a recognition logic array constructed to represent predetermined discrete time delay increments of said manifestations as said reference points.

3. A system according to claim 2 which includes means for sequentially applying said time of arrival pattern to said array in discrete time increments, said logic array providing a coarsely quantized time-variable manifestation corresponding to the location of said point.

4. A system according to claim 3 which also includes interpolation means for interpolating said time-variable manifestations, thereby to locate precisely said point in said space.

5. A system according to claim 1 which includes as said emitter a transmitter located at said point for transmitting signals to said sensor means.

6. A system according to claim 5 wherein each said sensor means includes a first receiver means for receiving said transmitted signals, a second receiver means for receiving a common time reference signal, and counting means for establishing a count signal corresponding to the time interval between said reference signal and said transmitted signal, thereby to provide a time of arrival count signal.

7. A system according to claim 6 which also includes means for transferring said time of arrival count signals from each said sensor means to said encoding means.

8. A system according to claim 7 wherein said encoding means includes a digital to analog converter means for converting each of said count signals into a time varying signal corresponding in time position to the location of said point.

9. A system according to claim 8 wherein said encoding means includes a clocked shift register for each said time varying signal for sequentially presenting said time varying signals to said comparator means only for predetermined time intervals after the arrival of each set of count signals.

10. A system according to claim 8 wherein said encoding means includes a clocked shift register for each said time varying signal for dividing each said time varying signal into increments, thereby to form a time of arrival pattern of signals for each said sensor means for presentation to said logic array.

11. A system according to claim 10 wherein said logic array is responsive to said time varying signal increments to provide quantized time-varying signals from reference points that are close to said point.

12. A system according to claim 11 which also includes interpolation means responsive to said quantized time varying signals for converting them to amplitude modulated signals corresponding to said point.

13. A system according to claim 3 wherein said manifestations are signals and wherein said logic array is responsive to said time varying signal increments to provide quantized time-varying signals from reference points that are close to said point.

14. A system according to claim 13 which includes display means responsive to said amplitude modulated signals for displaying the coordinates of said point.

15. A system according to claim 1 wherein said point is supplied with a means for generating manifestations.

16. A system according to claim 1 wherein three parameters define each said measured point, said space is geographic space, and said time of arrival patterns are related to the propagation time of waves between said emitter and each of said sensor means.

17. A system according to claim 16 wherein said encoding means includes a clocked shift register for each said time varying signal for dividing eacH said time varying signal into increments, thereby to form a time of arrival pattern of signals for each said sensor means for presentation to said logic array.

18. A system according to claim 17 wherein said logic array is responsive to said time varying signal increments to provide quantized time-varying signals from reference points that are closed to said point.

19. A system according to claim 18 which also includes interpolation means responsive to said quantized time varying signals for converting them to amplitude modulated signals corresponding to said point.