Electromagnetic location and display system and method

• US 20060267833A1
• Filed: 08/08/2006
• Published: 11/30/2006
• Est. Priority Date: 10/04/2004
• Status: Active Grant

• Current Assignee: Q-Track Corporation
• Original Assignee: Q-Track Corporation
• Inventors: Schantz, Hans Gregory, Langford, David Wesley
• Granted Patent: US 7,538,715 B2
• Time in Patent Office: Days
• US Class Current: 342/174
• CPC Class Codes: G01S 5/02524 Creating or updating the radio-map

Abstract

An unknown location for a transmitter/receiver is determined using a calibration process. An area is established with reference receivers at known locations and a mobile transmitter provides a location signal. An alternative embodiment uses reference transmitters and a mobile receiver. For calibration, the transmitter is placed at multiple measured locations and signal measurements are taken to generate a calibration map. Multiple signal measurements may be taken at each receiver, and multiple receivers may be used. In one embodiment, signal measurements include a near-field phase. In operation, one or more location signals are measured at one or more receivers. The measured signals are compared with the calibration maps to generate a set of comparison maps which are combined to generate a likelihood map. A likely region and most likely location are determined from the likelihood map and may be displayed relative to a map of the environment.

Claims

1. A system for locating an object within an area comprising

at locator unit located with said object;

at least one reference unit at a known location, said locator unit and said reference unit communicating at least one signal having at least one signal property.

a calibration map, said calibration map representing a plurality of expected values for said at least one signal property as a function of a possible location for said locator unit;

a comparison unit for comparing measurements of said signal property with said calibration map to generate a comparison map;

a combination unit for combining said comparison maps to generate a likelihood map;

a display for displaying said likelihood map.

2. The system of claim 1, wherein said locator unit is a transmitter and said at least one reference unit is a receiver.

3. The system of claim 1, wherein said locator unit is a receiver and said at least one reference unit is a transmitter.

4. The system of claim 1, wherein said at least one property of said at least one signal is a near field phase.

5. The system of claim 1, further including an interpolation function for interpolating between a plurality of measured calibration points to generate said calibration map.

6. The system of claim 5, wherein said interpolation function comprises a triangulation function.

7. The system of claim 1, further including a threshold unit for thresholding the likelihood map to generate a likely region, said display displaying said likely region.

8. The system of claim 7, wherein the likely region is displayed by using a contour plot or by using a color change.

9. The system of claim 8, wherein the color change includes a distinct color transition from the likely region to the remainder of the display.

10. The system of claim 1, further including a display of a most likely location based on an extreme value of said likelihood map or a centriod of said likely region.

11. A method for displaying an object location comprising:

generating a calibration dataset;

transmitting at least one location signal;

receiving said at least one location signal;

generating a likelihood map of an area showing the likelihood of said object location based on said receiving of said at least one location signal;

determining a likely region based on said likelihood map, said likely region representing a region within said likelihood map where said object is likely to be located;

displaying said likely region within a display of said area.

12. A method for determining a likely region for an object comprising:

generating a set of calibration maps for an area by the steps of;

transmitting a plurality of signals from a plurality of known transmitter locations;

receiving said plurality of signals and measuring a plurality of properties for each of said signals of said plurality of signals, said receiving being from known receiver locations;

recording a plurality of calibration maps, each said calibration map relating one of said measured properties to corresponding locations within said area.

transmitting a location signal;

receiving said location signal and measuring said plurality of properties for said location signal;

comparing each of said properties of said plurality of properties for said location signal with a corresponding said calibration map to generate a plurality of comparison maps;

combining said plurality of said comparison maps to generate a combination map;

determining said likely region, said likely region being a region within said combination map defined by a predetermined threshold.

13. The method of claim 12, wherein a location associated with said transmitting said location signal is unknown and the likely region represents a likely region for the unknown location.

14. The method of claim 12, wherein a location associated with said receiving of said location signal is unknown and the likely region represents a likely region for the unknown location.

15. The method of claim 12, wherein at least one of the properties of the received signal is a near field property.

16. The method of claim 12, further including the step of:

displaying the likely region.

17. The method of claim 16, wherein the step of displaying the likely region comprises displaying the likely region as a contour plot or a color plot.

18. The method of claim 17, wherein the likely region is shown using a distinct color change at the likely region boundary.

19. The method of claim 22, further including the step of:

displaying an extreme point of the combination map.

20. The method of claim 22, further including the step of:

displaying a centroid of the likely region.