METHOD AND SYSTEM FOR PROVIDING A GPS-BASED POSITION

• US 20100049376A1
• Filed: 08/19/2008
• Published: 02/25/2010
• Est. Priority Date: 08/19/2008
• Status: Active Grant

• Current Assignee: Navy The USA As Represented By The Secretary of The
• Original Assignee: Navy The USA As Represented By The Secretary of The
• Inventors: Schultz, Abraham
• Granted Patent: US 8,165,728 B2
• Time in Patent Office: Days
• US Class Current: 701/2
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 19/51 Relative positioning
• CPC Class Codes: G01S 5/0027 of actual mobile position, i.e. position determined on mobile
• CPC Class Codes: G01S 5/0072 Transmission between mobile stations, e.g. anti-collision systems
• CPC Class Codes: G01S 5/0284 Relative positioning

Abstract

A cooperative engagement group-position determining system employs a group of at least three cooperative units, for example a group of unmanned aerial vehicles (UAV'"'"'s), with each unit including a GPS system for determining a GPS-based position, an inter-distance measurement module for measuring a distance of the unit relative to at least one other unit, and a computer having a computer-readable storage medium encoded with a program algorithm for correcting the GPS-based position based on at least one relative distance between two units, providing an improved GPS-based position for the unit and for the group. The system can also include a ground controller, for example, for providing flight control for UAV'"'"'s.

Claims

1. A cooperative engagement group-position determining system, comprising:

a group of at least three cooperative units, wherein each said unit comprises;

i) a GPS system for determining a GPS-based position;

ii) an inter-distance measurement module for measuring a distance of the unit relative to at least one other unit; and

iii) a computer including a computer-readable storage medium encoded with a program algorithm that includes instructions for correcting the GPS-based position based on at least one relative distance between two units to thereby provide an improved GPS-based position for the unit and for the group.

2. A group-position determining system as in claim 1, wherein the algorithm comprises an iterative process for i) generating a set of position vectors for each unit to thereby obtain a set of computed positional data and inter-distances for each unit and ii) minimizing a mean square error between the inter-distances and the GPS-based position, thereby correcting the GPS-based position and providing the improved GPS-based position.

3. A group-position determining system as in claim 2, wherein the iterative process comprises repeating steps i) and ii) until a desired degree of convergence and a final converged estimate of positions of units is obtained.

4. A group-position determining system as in claim 3, wherein the GPS errors over all units in the cluster are averaged by applying a rigid body transformation of space to the final converged estimate of positions of units to thereby minimize an objective function of the type given by

E=D(A⁽ⁿ⁾, A)+D(B⁽ⁿ⁾, B)+D(C⁽ⁿ⁾, C)

where A⁽ⁿ⁾, B⁽ⁿ⁾ and C⁽ⁿ⁾ are the final converged estimate of positions of units.

5. A group-position determining system as in claim 1, wherein the group has at least four cooperative units.

6. A group-position determining system as in claim 3, wherein the units are unmanned aerial vehicles (UAV'"'"'s).

7. A group-position determining system as in claim 6, further comprising a ground controller for flight-controlling the UAV'"'"'s.

8. A radar system, comprising:

a plurality of at least four unmanned airborne platforms, each comprising;

i) a synthetic aperture radar system configured to exchange radar data with at least one of the other unmanned airborne platforms;

ii) an on-board GPS system for linking with a satellite-based GPS system to compute an individual GPS-based position;

iii) an inter-distance computing module for measuring an inter-distance to at least one other platform; and

iv) a computer including a computer-readable storage medium encoded with a program algorithm that includes instructions for a) applying the inter-distance measurement to at least one individual GPS-based position to thereby provide an improved GPS-based group position, and b) constructing an improved SAR radar image based on the improved GPS-based group position.

9. A radar system as in claim 8, wherein the algorithm comprises an iterative process for i) generating a set of position vectors for each unit to thereby obtain a set of computed positional data and inter-distances for each unit and ii) minimizing a mean square error between the inter-distances and the GPS-based position, thereby correcting the GPS-based position and providing the improved GPS-based position.

10. A radar system as in claim 9, wherein the iterative process comprises repeating steps i) and ii) until a desired degree of convergence and a final converged estimate of positions of units is obtained.

11. A radar system as in claim 10, wherein the GPS errors over all units in the cluster are averaged by applying a rigid body transformation of space to the final converged estimate of positions of units to thereby minimize an objective function of the type given by

E=D(A⁽ⁿ⁾, A)+D(B⁽ⁿ⁾, B)+D(C⁽ⁿ⁾, C)

where A⁽ⁿ⁾, B⁽ⁿ⁾ and C⁽ⁿ⁾ are the final converged estimate of positions of units.

12. A radar system as in claim 11, wherein the unmanned airborne platforms are UAV'"'"'s.

13. A radar system as in claim 12, further comprising a ground controller for flight-controlling the UAV'"'"'s.

14. A method of correcting a GPS-based position for a cooperative engagement group, comprising:

deploying a group of at least three cooperative units, wherein each said unit comprises;

i) a GPS system for determining a GPS-based position;

ii) an inter-distance measurement module for measuring a distance of the unit relative to at least one other unit; and

iii) a computer including a computer-readable storage medium encoded with a program algorithm that includes instructions for correcting the GPS-based position based on at least one relative distance between two units;

obtaining an initial GPS-based position for each of the units;

measuring an inter-distance between at least two of the units; and

correcting the initial GPS-based position for each unit based on at least one relative distance between two units to thereby provide an improved GPS-based position for the unit and for the group.

15. A method as in claim 14, wherein the inter-distance is measured between each unit and each remaining unit and the GPS-based position is corrected based on all inter-distance measurements thus obtained.

16. A method as in claim 15, wherein the correcting comprises an iterative process for i) generating a set of position vectors for each unit to thereby obtain a set of computed positional data and inter-distances for each unit and ii) minimizing a mean square error between the inter-distances and the GPS-based position, thereby correcting the GPS-based position and providing the improved GPS-based position.

17. A method as in claim 16, wherein the iterative process comprises repeating steps i) and ii) until a desired degree of convergence and a final converged estimate of positions of units is obtained.

18. A method as in claim 17, wherein the GPS errors over all units in the cluster are averaged by applying a rigid body transformation of space to the final converged estimate of positions of units to thereby minimize an objective function of the type given by

E=D(A⁽ⁿ⁾, A)+D(B⁽ⁿ⁾, B)+D(C⁽ⁿ⁾, C)

where A⁽ⁿ⁾, B⁽ⁿ⁾ and C⁽ⁿ⁾ are the final converged estimate of positions of units.

19. A method as in claim 18, wherein each of the units is a UAV having an onboard SAR for obtaining an SAR radar image, and further comprising the step of constructing an improved SAR radar image based on the improved GPS-based group position.

20. A method as in claim 19, further comprising flight-controlling the UAV'"'"'s using a ground control system.