LONG-RANGE ACOUSTICAL POSITIONING SYSTEM ON CONTINENTAL SHELF REGIONS

• US 20120092964A1
• Filed: 10/13/2011
• Published: 04/19/2012
• Est. Priority Date: 10/13/2010
• Status: Active Grant

• Current Assignee: University of Delaware
• Original Assignee: University of Delaware
• Inventors: Badiey, Mohsen, Katsnelson, Boris
• Granted Patent: US 9,013,959 B2
• Time in Patent Office: Days
• US Class Current: 367/127
• CPC Class Codes: G01S 5/30 Determining absolute distances from a plurality of spaced points of known location

Abstract

Methods and systems for determining a geophysical position of an object in an underwater channel are provided. Acoustic signals from at least two sources are received by a receiver of the object. The acoustic signals have a frequency corresponding to at least one waveguide mode associated with the underwater channel, where the acoustic signals are transmitted at predetermined transmission times. An arrival time for the at least one waveguide mode is determined from the received signals, based on the predetermined transmission times. The geophysical position is determined based on the arrival time and a modal group velocity for the at least one waveguide mode.

Claims

1. A method for determining a geophysical position of an object in an underwater channel, the method comprising:

receiving, by the object, acoustic signals from at least two sources including a frequency corresponding to at least one waveguide mode associated with the underwater channel, the acoustic signals being transmitted at respective predetermined transmission times;

determining an arrival time for the at least one waveguide mode from the received acoustic signals, based on the respective predetermined transmission times; and

determining the geophysical position based on the arrival time and a modal group velocity for the at least one waveguide mode.

2. The method according to claim 1, further comprising determining a sound speed profile of each source, wherein the modal group velocity is determined based on the sound speed profile of each source.

3. The method according to claim 2, wherein the sound speed profile of each source is determined as a function of temperature relative to depth of the underwater channel.

4. The method according to claim 3, wherein the determining of the sound speed profile of each source includes:

measuring the sound speed profile of each source using a thermistor string in an operation area proximate the at least two sources.

5. The method according to claim 3, wherein the determining of the sound speed profile of each source includes:

estimating the respective sound speed profile based on predetermined temperature values for an operation area proximate the at least two sources.

6. The method according to claim 1, wherein the geophysical position of the object is determined relative to the at least two sources for a range of less than or equal to about 100 km.

7. A receiver disposed on an object in an underwater channel comprising:

a receiving element for receiving acoustic signals from at least two sources, each acoustic signal including a frequency corresponding to at least one waveguide mode associated with the underwater channel, the acoustic signals being transmitted at respective predetermined transmission times; and

a processor for determining an arrival time for the at least one waveguide mode from the received acoustic signals, based on the respective predetermined transmission times and for determining a geophysical position of the object based on the arrival time and a modal group velocity for the at least one waveguide mode.

8. The receiver according to claim 7, further comprising a clock synchronized with respective clocks of the at least two sources.

9. The receiver according to claim 7, further comprising a memory for storing at least one of the predetermined transmission time for each source and the modal group velocity for the at least one waveguide mode.

10. The receiver according to claim 7, further comprising a transmitting element for transmitting a further acoustic signal to a remote observer,

wherein the further acoustic signal and one or more of the acoustic signals from the respective at least two sources are received by the remote observer and used to determine the geophysical position of the object.

11. The receiver according to claim 7, wherein the processor determines the modal group velocity for the at least one waveguide mode based on a sound speed profile for each source.

12. The receiver according to claim 11, wherein the sound speed profile is a function of temperature relative to depth of the underwater channel.

13. The receiver according to claim 7, further comprising a depth sensor for determining a depth of the object in the underwater channel.

14. The receiver according to claim 7, wherein the geophysical position of the object is determined relative to the at least two sources for a range of less than or equal to about 100 km.

15. The receiver according to claim 7, wherein the object includes an autonomous underwater vehicle (AUV).

16. An acoustical positioning system for an underwater channel comprising:

at least two sources for transmitting acoustic signals, each acoustic signal including a frequency corresponding to at least one waveguide mode associated with the underwater channel, the acoustic signals being transmitted at respective predetermined transmission times; and

a receiver disposed on an object for receiving the acoustic signals from the at least two sources, the receiver including;

a processor for determining an arrival time for the at least one waveguide mode from the received acoustic signals, based on the respective predetermined transmission times and for determining a geophysical position of the object based on the arrival time and a modal group velocity for the at least one waveguide mode.

17. The system according to claim 16, wherein each of the at least two sources and the receiver includes clocks synchronized with each other.

18. The system according to claim 16, wherein each source includes a memory for storing at least one of the respective predetermined transmission time and a sound speed profile associated with the source.

19. The system according to claim 16, wherein each source includes a further processor for determining a sound speed profile associated with the respective source, the sound speed profile being a function of a temperature relative to a depth of the underwater channel.

20. The system according to claim 19, wherein the processor of the receiver determines the modal group velocity for the at least one waveguide mode based on the sound speed profile for each source.

21. The system according to claim 19, wherein the at least two sources are proximate to at least one thermistor string, and, the further processor determines the sound speed profile for each source based on temperature values from the at least one thermistor string.

22. The system according to claim 19, wherein the further processor determines the sound speed profile based on predetermined temperature values for an operation area proximate to the at least two sources.

23. The system according to claim 19, wherein:

the receiver includes a transmitting element for transmitting a further acoustic signal,

one or more of the at least two sources includes a receiving element for receiving the further acoustic signal and the acoustic signals from the remaining sources, and

the further processor determines the geophysical position of the object.

24. The system according to claim 16, wherein one or more of the at least two sources includes an array of sources for transmitting respective acoustic signals.

25. The system according to claim 16, wherein the frequency corresponding to the at least one waveguide mode is less than or equal to about 500 Hz.

26. The system according to claim 16, wherein each source transmits the respective acoustic signal at a same time.

27. The system according to claim 16, wherein one or more of the at least two sources transmits the respective acoustic signal at a different time.

28. The system according to claim 16, wherein one or more of the at least two sources transmits the respective acoustic signal with a further frequency corresponding to a different waveguide mode.