System and method for increased indoor position tracking accuracy

• US 10,135,667 B1
• Filed: 06/08/2012
• Issued: 11/20/2018
• Est. Priority Date: 06/08/2011
• Status: Active Grant

• Current Assignee: Kerry L. Greer
• Original Assignee: Kerry L. Greer
• Inventors: Greer, Kerry L.
• Primary Examiner(s): Wang-Hurst, Kathy
• Assistant Examiner(s): Hannan, B. M. M
• Application Number:
  US13/492,411
• Time in Patent Office: 2,356 Days
• Field of Search: 4554042, 455440, 455448, 4554563, 4554566, 4554142, 455430, 4554351, 455566, 4554561-457, 370328, 370329, 370331, 370332, 370400, 370252, 342126, 342450-465
• CPC Class Codes: G01S 1/24 the synchronised signals being pulses or equivalent modulations on carrier waves and the transit times being compared by measuring the difference in arrival time of a significant part of the modulations , e.g. LORAN systems
• CPC Class Codes: G01S 1/245 Details of receivers cooperating therewith, e.g. determining positive zero crossing of third cycle in LORAN-C
• CPC Class Codes: G01S 5/00 Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using active systems G01S13/00, G01S15/00, G01S17/00
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308
• CPC Class Codes: H04L 67/52 specially adapted for the location of the user terminal
• CPC Class Codes: H04L 67/535 Tracking the activity of the user network monitoring arrangements H04L43/00; recording of computer activity G06F11/34
• CPC Class Codes: H04W 4/029 Location-based management or tracking services
• CPC Class Codes: H04W 4/16 Communication-related supplementary services, e.g. call-transfer or call-hold
• CPC Class Codes: H04W 4/33 for indoor environments, e.g. buildings
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A method and system for increased position tracking resolution in a localized environment for use in GPS-denied areas such as within buildings or enclosed structures, comprising: multiple reference nodes each transmitting a synchronization pulse to a multitude of body-worn or device-mounted receiving units; a high speed clock circuit in each receiver capable of measuring the Time Difference of Arrival of said sync pulses to the resolution needed for precise positioning; a central processing computer used to calculate actual position of the receiving units relative to some fixed reference point; and a display system to monitor the position of the receiving units in real time as they move around within the target area overlaid onto available GIS data or building CAD drawings.

Claims

1. A position tracking system for tracking at least one mobile module suitable for a defined GPS-denied target area, the position tracking system including:

at least three reference modules in a GPS permitted area surrounding said defined GPS-denied target area, where said at least three reference modules are configured to periodically broadcast reoccurring synchronization pulses simultaneously driven off the 1 Pulse-Per-Second out put from differential GPS;

said at least one mobile module having a local oscillator using a clock counter running at least at 1 GHz for measuring each pulse wave form within up to a wavelength and at least one receiver configured to receive said synchronization pulses and record a time of receipt of each of the reoccurring said synchronization pulses from each of said at least three reference modules as referenced by said at least one mobile module'"'"'s own local oscillator, wherein said at least one mobile module records time of arrival data from the each of the reoccurring said synchronization pulses and said time of arrival data necessary to calculate a specific physical location of said at least one mobile module relative to said at least three reference modules and measure said time of arrival data to a resolution needed for precision positioning; and

said at least one mobile module having at least one receiver which calculates said time of arrival data using only a differential time reference measurement between the receipt of the each of the reoccurring said synchronization pulses as referenced by said at least one mobile module'"'"'s own local oscillator, thereby eliminating the need for coherent time synchronization between said at least three reference modules and said at least one receiver, wherein the broadcast of the reoccurring said synchronization pulses is driven off the 1 Pulse-Per-Second output from the Differential GPS to lock a starting time of the each of the reoccurring said synchronization pulses;

wherein the each of said at least three reference modules broadcast the each of the reoccurring said synchronization pulses simultaneously on a discrete sub-channel of a frequency channel utilization.

2. The position tracking system as in claim 1, wherein a graphical representation is overlaid onto map showing features of the target area.

3. The position tracking system as in claim 1, wherein said at least one mobile module has at least three receivers.

4. The position tracking system as in claim 1, wherein three reference modules are utilized.

5. The position tracking system as in claim 1, wherein four reference modules are utilized.

6. The position tracking system as in claim 1, wherein the each of said at least three reference modules establishes its respective absolute geographic position using Differential GPS receivers.

7. The position tracking system as in claim 1, wherein said at least one mobile module has four receivers.

8. The position tracking system as in claim 1, wherein said synchronization pulses pulse data comprises a measurement of said Time of Arrival of said synchronization pulses from said at least three reference modules.

9. The position tracking system as in claim 1, including:

a command node configured to electronically communicate with said at least three reference modules and said at least one mobile module and to coordinate operation of said at least three reference modules, wherein coordinating the operation of said at least three reference modules and said at least one mobile module determines the specific physical location of said at least one mobile module; and

a display device having a graphical representation of the specific physical location of said at least one mobile module relative to said at least three reference modules.

10. A position tracking method for locating at least one mobile module within a GPS:

denied target area suitable for a defined GPS-denied target area, the position tracking method comprising the steps of;

providing inside said defined GPS-denied target area the at least one mobile module having a synchronization pulse receiver and a local oscillator;

providing in a GPS permitted area at least first, second, and third reference modules, said at least first, second, and third reference modules configured to periodically broadcast simultaneously first, second, and third reoccurring synchronization pulses respectively to enhance an accuracy of location and to reset cumulative error to zero at a start of each periodical broadcast;

receiving said at least first, second, and third reference modules reoccurring synchronization pulses in the at least one mobile module;

recording exact time of receipt of each of said first, second, and third reoccurring synchronization pulses from each of said at least first, second, and third reference module; and

the at least one mobile module'"'"'s own local oscillator using a clock counter running at least at 1 GHz measuring time of arrive data of the each of said first, second, and third reoccurring synchronization pulses from said at least first, second, and third reference modules to measure the time of arrival data to a resolution necessary for measuring the each of said first, second, and third reoccurring synchronization pulses within up to a wave length for precision positioning;

providing known accuracy specific location of each of said at least first, second, and third reference module;

providing a display;

configuring said at least first, second, and third reference modules, wherein the step of configuring said at least first, second, and third reference modules comprises placing said at least first, second, and third reference modules so that the each of said at least first, second and third reference module is located around a perimeter of the target area in said GPS permitted area and establishing their respective geographical positions based upon differential GPS receivers or via fixed site survey data;

broadcasting by the each of said at least first, second, and third reference modules, said first, second, and third reoccurring synchronization pulses simultaneously; and

measuring by the at least one mobile module and its local oscillator time difference between said first, second, and third reoccurring synchronization pulses, and using the time difference to calculate location of the at least one mobile module;

wherein the each of said first, second, and third recurring synchronization pulses is driven off the 1 Pulse-Per-Second output from the Differential GPS to lock a starting time of each of said first, second, and third simultaneous synchronization pulses; and

wherein the each of said at least first, second, and third reference module broadcast said first, second, and third reoccurring synchronization pulse on a discrete sub-channel of the frequency channel utilized; and

the at least one mobile module has at least three receivers for receiving said first, second, and third reoccurring synchronization pulses from said at least first, second, third reference modules.

11. The position tracking method as in claim 10, wherein:

four reference modules are utilized; and

the at least one mobile module has four receivers.