Satellite radio ranging velocity navigation

• US 3,941,984 A
• Filed: 07/05/1973
• Issued: 03/02/1976
• Est. Priority Date: 07/05/1973
• Status: Expired due to Term

• Current Assignee: Halliburton Company
• Original Assignee: Texas Instruments, Inc.
• Inventors: Chappell, Peter, Gilbert, Gerald M., Hicks, Burnette W.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Blum, T. M.
• Application Number:
  US05/376,481
• Time in Patent Office: 971 Days
• Field of Search: 340/27 NA, 340/27 SS, 343/100 ST, 343/112 S, 343/103, 235/150.27, 235/150.26, 235/150.24, 73/178
• US Class Current: 701/219
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G06F 7/548 Trigonometric functions; Co-ordinate transformations

Abstract

In an integrated satellite navigation system where satellite fixes periodically establish the position of a ship plying a course within the range of a chain of radio ranging stations, ship velocities are accurately determined in the interval between satellite fixes to chart the course between fixes by establishing difference values between successive RF signal transit times for each of a plurality of radio ranging stations. A set of functions dependent upon the difference values for transit times related to each station is stored, retaining the most recent and discarding the most aged of the set. Velocity signals representative of the motion of the ship are then periodically generated by utilization of the sets of difference functions. Preferably, the sets of difference functions are modified to give the most recent members of each set the greater weight.

Claims

1. In an integrated satellite navigation system where satellite fixes periodically establish the position of a ship plying a course within the range of a chain of radio ranging stations and wherein ship velocities must be accurately determined in the interval between satellite fixes in order to chart said course, the combination which comprises:

means for measuring difference values between successive RF signal transit times for each of a plurality of said stations,

means to store a set of functions, one for each of said stations, dependent upon said difference values for transit times related to each said station,

means to update each said set with new difference values for each said station while discarding the most aged of said functions in the corresponding set, and

a least mean squares generator utilizing said sets periodically to generate velocity signals representative of the motion of said ship.

2. The combination set forth in claim 1 wherein weighting means are provided to modify said set of functions to weight the most recent function greater than the most aged function.

3. The combination set forth in claim 2 wherein said weighting means is linear.

4. The combination set forth in claim 1 wherein control means sample said transit times at a high rate and said generator produces said velocity signals at a lower rate.

5. The combination set forth in claim 4 wherein said control means operates at said high rate of the order of four times said lower rate.

6. A system for determining ship velocity from radio ranging signals which comprises:

a. means for generating successive radio range signals at a selected rate, each representative of the radio range between said ship and one of at least two fixed base stations,

b. signal process means for comparing each range signal from each base station with its next preceding signal to determine a difference signal,

c. means for storing a predetermined number of ship velocity related functions each dependent upon one of a like number of the most recent of said signals, and

d. processor means for generating output signals representative of ship velocity utilizing sets of said stored functions whose difference signal is below a limit indicative of a predetermined change in ship velocity in the interval between successive range signals.

7. A system for aiding in navigation of a marine vessel in reach of a plurality of base radio ranging stations which comprises:

a. a radio ranging mobile station means on said vessel for generating at least two sets of radio range signals, one set for each of two base stations with each set comprising a real time series of N successive signals,

b. comparison means connected to receive and compare each signal in each series with its next preceding signal to generate difference signals, and

c. processing means operating on sets of said N range signals while excluding any range signal for which said difference signal exceeds a preset limit to generate signals representative of velocity of said vessel.

8. A system for determining ship velocity from radio ranging signals which comprises:

a. means for generating successive radio range signals at a selected rate, each representative of the radio range between said ship and one of at least two fixed base stations,

b. means to store and compare the two most recent of said range signals for each said base station to produce difference signals,

c. means for storing a predetermined number of ship velocity related functions each dependent upon one of a like number of the most recent of said signals, and

d. means for generating output signals representative of ship velocity utilizing said stored functions while excluding any stored function whose related difference function exceeds a predetermined limit.

9. In an integrated satellite navigation system where satellite fixes periodically establish the position of a ship plying a course within the range of a chain of radio ranging stations and wherein ship velocities must be accurately determined in the interval between satellite fixes in order to chart said course, the method which comprises:

a. establishing difference values between successive RF signal transit times for each of a plurality of said stations,

b. for each of said stations storing a set of functions dependent upon successive difference values between transit times related to each said station while retaining the most recent function and discarding the most aged function in the corresponding set, and

c. periodically generating velocity signals representative of the motion of said ship by a least mean squares utilization of said sets.

10. In an integrated satellite navigation system where satellite fixes periodically establish the position of a ship plying a course within the range of a chain of radio ranging stations and wherein ship velocities must be accurately determined in the interval between satellite fixes in order to chart said course, the method which comprises:

a. establishing difference signals representative of the differences between transit times of successive Loran transmissions between said ship and each of a plurality of said stations,

b. for each of said stations storing a set of functions dependent upon the difference signals related to each said station while retaining the most recent function and discarding the most aged function in the corresponding set, and

c. periodically generating velocity signals representative of the motion of said ship by a least mean squares utilization of said sets.

11. The method of claim 10 wherein the ship-station transit time is sampled at a high rate and velocity signals are generated at a low rate.

12. The method of claim 10 in which a ship-station transit time is sampled each second and velocity signals are generated each four second interval.

13. The method of claim 10 in which each said set of elements are of the order of 40 in number and whereby said velocity signals each reflects 40 samples, one per second, on a least mean square utilization of Loran transit time differences.

14. In determining ship velocity from radio ranging signals the method which comprises:

a. generating successive radio range signals at a selected rate, each representative of the radio range between said ship and one of at least two fixed base stations,

b. for each base station comparing each range signal therefrom with its next preceding signal to determine difference signal,

c. for each said station storing a predetermined number of ship velocity related functions each dependent upon one of a like number of the most recent of said signals, and

d. generating output signals representative of ship velocity utilizing said stored functions while excluding any stored function whose related difference signal is of magnitude to indicate a predetermined excessive change in ship velocity in the interval between generation of range signals.

15. In navigating a marine vessel in reach of a plurality of base radio ranging stations the method which comprises:

a. generating at said vessel at least two sets of radio range signals, one set for each of two base stations with each set comprising a real time series of N successive signals,

b. comparing each signal in each series with its next preceding signal to generate difference signals, and

c. generating signals representative of vessel velocity utilizing sets of said N range signals while excluding any range signal for which said difference signal exceeds a predetermined limit.

16. The method of claim 15 in which signals representative of bearings from said vessel to each said base station are generated and employed in generation of said velocity signals.

17. The method of claim 15 in which N is of the order of 40.