SPACE-TIME CALIBRATION SYSTEM AND METHOD

• US 20090313370A1
• Filed: 12/07/2007
• Published: 12/17/2009
• Est. Priority Date: 12/07/2006
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: ZULU Time LLC
• Inventors: Rhoads, Geoffrey
• Granted Patent: US 9,791,545 B2
• Time in Patent Office: Days
• US Class Current: 709/224
• CPC Class Codes: G01S 5/18 using ultrasonic, sonic, or infrasonic waves
• CPC Class Codes: G01S 5/26 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/28 takes precedence

Abstract

A space-time calibration system and method implement space-time solutions, in which, in one preferred embodiment, a single node determines its own space-time solutions based on other network nodes with which the single node communicates. In other preferred embodiments, space-time solutions for the node can be generated using other resources in the network. The disclosed system and method enable reliable, precise object positioning particularly for environments where the Global Positioning System (GPS) is blocked or subject to interference such as within the urban core.

Claims

1. A space-time calibration method of determining position and timing information relating to one or more nodes of multiple nodes occupying locations in a spatial region and communicating with one another, comprising:

providing in a spatial region multiple nodes including transmitting nodes and receiving nodes, the transmitting nodes producing ping transmit events and the receiving nodes producing ping receive events by receiving and associating receive count stamps to the ping transmit events, the receive count stamps based on independent clocks operating in the receiving nodes.

developing pung signals representing a record of ping events relating to associated ones of the ping transmit events and the ping receive events during a data recording time interval, the record for each receiving node including the receive count stamps corresponding to the ping receive events produced during the data recording time interval; and

processing the pung signals to determine, for each one of a number of nodes of the multiple nodes, location information corresponding to a location occupied by the node in the spatial region.

2. The method of claim 1, further comprising associating with transmit count stamps the ping transmit events produced by the transmitting nodes, the transmit count stamps based on independent clocks operating in the transmitting nodes and characterized by clock instability functions, and in which the ping transmit events received by the receiving nodes include count-stamped ping transmit events.

3. The method of claim 1, in which the number of nodes includes a set of transmit nodes, and in which the processing of the pung signals determines from the location information a spatial distribution of member nodes of the set of transmit nodes in the spatial region.

4. The method of claim 1, in which the number of nodes includes a set of receive nodes, and in which the processing of the pung signals determines from the location information a spatial distribution of member nodes of the set of receive nodes in the spatial region.

5. The method of claim 1, in which the number of nodes includes a set of duplex nodes, and in which the processing of the pung signals determines from the location information a spatial distribution of member nodes of the set of duplex nodes in the spatial region.

6. The method of claim 2, in which the record of the ping events includes differential count stamp values corresponding to differences between the receive count stamps and the associated transmit count stamps.

9. The method of claim 1, further comprising deriving a system clock from the clock instability functions of the multiple nodes.

10. The method of claim 1, in which at least one of the number of multiple nodes changes location with time to describe a path of motion characterized by concatenated path segments having start and finish locations, and the processing of pung signals further comprises determining from a previous one of the path segments a corrected start location of and a corrected clock for a current one of the path segments to reduce cumulative error in the determination of the location occupied by the node and the clock instability function of the clock operating in the node.

11. The method of claim 10, in which the processing of the pung signals generates a referenced solution for the corrected start location and corrected clock.

20. The method of claim 1, in which the receive count stamps are characterized by clock instability functions, and the processing of the pung signals further comprises determining, for each one of a number of nodes of the multiple nodes, the clock instability function characterizing the clock operating in the node.

7. and 8. (canceled)

12. A space-time calibration engine, comprising:

an input configured to receive count-stamped information signals propagating through a medium from multiple nodes occupying a spatial region, the multiple nodes including source and receiving nodes operating with independent clocks characterized by clock instability functions, and the count-stamped information signals carrying information relating to transmit and receive events of the source and receiving nodes; and

a processor determining from information carried by the count-stamped information signals, for each one of a number of the multiple nodes, location information corresponding to a location occupied by the node in the spatial region and the clock instability function characterizing the clock operating in the node.

13. The space-time calibration engine of claim 12, in which at least one of the count-stamped information signals propagating from the multiple nodes is generated remotely from the node.

14. The space-time calibration engine of claim 12, in which at least one of the count-stamped information signals propagating from the multiple nodes is generated within the node.

15. The space-time calibration engine of claim 12, in which at least one of the number of multiple nodes changes location with time to describe a path of motion characterized by concatenated path segments having start and finish locations, and in which the processor determines from a previous one of the path segments a corrected start location of and a corrected clock for a current one of the path segments to reduce cumulative error in the determination of the location occupied by the node and the clock instability function of the clock operating in the node.

16. The space-time calibration engine of claim 15, in which the processor generates a referenced solution for the corrected start location and corrected clock.

17. The space-time calibration engine of claim 12, in which the input and the processor are implemented at a remote location from the locations of the multiple nodes.

18. The space-time calibration engine of claim 12, further comprising multiple ones of the input and multiple ones of the processor recited in claim 12, and in which each of at least some of the multiple nodes is implemented with one of the inputs and one of the processors.

19. The space-time calibration engine of claim 12, in which the processor determines the location information and the clock instability function by generating, over solution intervals, solutions indicating changes in location occupied by the node and changes in the clock instability function characterizing the clock operating in the node.