Method and system of triangulating an object

• US 7,151,480 B2
• Filed: 01/03/2005
• Issued: 12/19/2006
• Est. Priority Date: 07/03/2002
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Jeppsson, Mikael, Wall, Per
• Primary Examiner(s): Pihulic, Dan
• Application Number:
  US11/027,686
• Publication Number:
  US 20050174287A1
• Time in Patent Office: 715 Days
• Field of Search: 342/125, 342/450, 356/463, 367/118
• US Class Current: 342/126
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders

Abstract

A method and a system of triangulating an object by means of at least two sensors. Each sensor is placed in a respective local reference system. Each of the at least two sensors at least provide a bearing to the object in their respective local reference system. According to the invention a triangulation reference system is created. The triangulation reference system is different to any one of the local reference systems and suitably such that at least two local reference systems are rotated more in relation to each other than each one is in relation to the triangulation reference system. Sensor positions and bearings are transformed into the triangulation reference system where the triangulation is performed. Suitably the triangulated position is then transformed into a desired reference system.

Claims

1. A method of triangulating an object by means of at least two sensors, each sensor being placed in a respective local reference system, each of the at least two sensors at least providing a bearing to the object in their respective local reference system, characterized in that the method comprises the steps of:

determining a triangulation reference system;

calculating a triangulation transformation matrix from each sensor'"'"'s local reference system to the triangulation reference system;

calculating an object transformation matrix from the triangulation reference system to an object reference system;

for each sensor used, determining at least a bearing to the object in a respective local reference system;

for each determined bearing to the object in a respective local reference system, calculating a corresponding bearing in the triangulation reference system by means of a corresponding calculated triangulation transformation matrix;

triangulating the object in the triangulation reference system by means of the calculated bearings in the triangulation reference system, by

transforming a position of the triangulated object in the triangulation reference system to a position of the triangulated object in the object reference system by means of the calculated object transformation matrix.

2. The method of triangulating an object according to claim 1, characterized in that the step of determining a triangulation reference system, determines a triangulation reference system that is at least substantially symmetrically oriented between the local reference systems of the sensors, in such a way that at least two local reference systems are rotated more in relation to each other than each one is in relation to the triangulation reference system.

3. The method of triangulating an object according to claim 1, characterized in that the local reference systems are defined by the geographical location of each respective sensor, in such a way that a plane of each respective local reference system is perpendicular to a normal of the surface where each respective sensor is located.

4. The method of triangulating an object according to claim 1, characterized in that the step of determining a triangulation reference system and the step of calculating a triangulation transformation matrix from each sensor'"'"'s local reference system to the triangulation reference system, are performed when a local reference system of at least one of the sensors change.

5. The method of triangulating an object according to claim 1, characterized in that the relationships between the triangulation reference system and each of the local reference systems are all known.

6. The method of triangulating an object according to claim 1, characterized in that the triangulation reference system and each of the local reference systems are all known in relation to a common reference system.

7. The method of triangulating an object according to claim 6, characterized in that the step of calculation the triangulation transformation matrices uses the common reference system to determine the relationship between the triangulation reference system and each one to the local reference systems.

8. The method of triangulating an object according to claim 6, characterized in that the step of calculating the triangulation transformation matrices uses the common reference system to determine the transformation matrices, whereby transformation matrices to and from the common reference system in relation to the triangulation reference system and each one of the local reference systems are first calculated, from which matrices the triangulation transformation matrices from each sensor'"'"'s local reference system to the triangulation reference system are calculated.

9. The method of triangulating an object according to claim 1, characterized in that the sensors only provide a bearing and/or the triangulation only takes into account provided bearings, and in that the triangulation reference system and each one of the local reference systems are planes.

10. The method of triangulating an object according to claim 9, characterized in that the step of calculating the triangulation transformation matrices from each sensor'"'"'s local reference system to the triangulation system and the step of calculating a corresponding bearing in the triangulation reference system involves a plane projection of each sensor location and determined bearing to the object from each respective local reference system to the triangulation reference system.

11. The method of triangulating an object according to claim 9, characterized in that at least one of the sensors provide an elevation to the object, and in that the triangulation reference system and at least the local reference systems of the sensor that provides the elevation are three dimensional reference systems, and in that a height of the object in the triangulation reference system is determined when the object has been triangulated.

12. The method of triangulating an object according to claim 1, characterized in that each of the sensors provide a bearing and an elevation, and in that the triangulation reference system and each one of the local reference systems are three dimensional reference systems.

13. The method of triangulating an object according to claim 12, characterized in that the step of triangulating the object in the triangulation reference system by means of the calculated bearings in the triangulation reference system, uses uncertainty cones about each calculated bearing for the triangulation of the object.

14. A system arranged to triangulate an object by means of at least two sensors, each sensor being placed in a respective local reference system, each of the at least two sensors at least providing a bearing to the object in their respective local reference system, characterized in that the system comprises:

means arranged to determine a triangulation reference system;

means arranged to calculate a triangulation transformation matrix from each sensor'"'"'s local reference system to the triangulation reference system;

means arranged, for each sensor used, to determine at least a bearing to the object in a respective local reference system;

means arranged to, for each determined bearing to the object in a respective local reference system, calculate a corresponding bearing in the triangulation reference system by means of a corresponding calculated triangulation transformation matrix;

means arranged to triangulate the object in the triangulation reference system by means of the calculated bearings in the triangulation reference system, and

means arranged to calculate an object transformation matrix from the triangulation reference system to an object reference system;

means arranged to transform a position of the triangulated object in the triangulation reference system to a position of the triangulated object in the object reference system by means of the calculated object transformation matrix.

15. The system according to claim 14, characterized in that the means arranged to determine a triangulation reference system, determines a triangulation reference system that is at least substantially symmetrically oriented between the local reference systems of the sensors, in such a way that at least two local reference systems are rotated more in relation to each other than each one is in relation to the triangulation reference system.

16. The system according to claim 14, characterized in that the local reference systems are defined by the geographical location of each respective sensor, in such a way that a plane of each respective local reference system is perpendicular to a normal of the surface where each respective sensor is located.

17. The system according to claim 14, characterized in that the means arranged to calculate the triangulation transformation matrices uses a common reference system to determine the transformation matrices, whereby transformation matrices to and from the common reference system in relation to the triangulation reference system and each one of the local reference systems are first calculated, from which matrices the triangulation transformation matrices from each sensor'"'"'s local reference system to the triangulation reference system are calculated.

18. The system according to claim 14, characterized in that the sensors only provide a bearing and/or the triangulation only takes into account provided bearings, and in that the triangulation reference system and each one of the local reference systems are planes.

19. The system according to claim 18, characterized in that the means arranged to calculate the triangulation transformation matrices from each sensor'"'"'s local reference system to the triangulation system and the means arranged to calculate a corresponding bearing in the triangulation reference system involves a plane projection of each sensor location and determined bearing to the object from each respective local reference system to the triangulation reference system.

20. The system according to claim 18, characterized in that at least one of the sensors provide an elevation to the object, and in that the triangulation reference system and at least the local reference systems of the sensor that provides the elevation are three dimensional reference systems, and in that a height of the object in the triangulation reference system is determined when the object has been triangulated.