Computer workstation tool for displaying performance estimate of tagged object geo-location system for proposed geometry layout of tag transmission readers

• US 6,366,242 B1
• Filed: 07/27/2000
• Issued: 04/02/2002
• Est. Priority Date: 01/21/1997
• Status: Expired due to Term

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Wherenet Corporation (Zebra Technologies Corporation)
• Inventors: Boyd, Robert W., Stryker, David J., Belcher, Donald K.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US09/626,021
• Time in Patent Office: 614 Days
• Field of Search: 342/450, 342/451
• US Class Current: 342/450
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: G01S 1/0428 Signal details
• CPC Class Codes: G01S 13/767 Responders; Transponders teaching or practice apparatus for gun-aiming or gun-laying using reflecting targets or active targets F41G3/26
• CPC Class Codes: G01S 13/82 wherein continuous-type signals are transmitted
• CPC Class Codes: G01S 13/825 with exchange of information between interrogator and responder
• 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 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0269 Inferred or constrained positioning, e.g. employing knowledge of the physical or electromagnetic environment, state of motion or other contextual information to infer or constrain a position
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• 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: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10079 the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions

Abstract

A reader geometry visualization tool for a geo-location system technician'"'"'s personal computer is operative to display a map of an asset management environment. The technician interactively places and manipulates a distribution of tag transmission readers and any potential impairments to RF transmissions on the map. The locations of the readers (and any impairments) are coupled as input parameters to a mathematical model of a tag-based geo-location system. The performance of the map-parameterized geo-location system model is then computed as a geometric dilution of precision (gdop) value for the intended object coverage area. The computed (gdop) performance is visually characterized on the displayed map, as by way of different colors to indicate how accurately the proposed reader geometry will enable the system to locate objects anywhere in the coverage area.

Claims

1. A method of operating a computer workstation to configure a system for locating objects within a monitored environment, wherein transmissions from tags with said objects are to be detected at a plurality of spaced apart tag transmission readers for said monitored environment, and outputs of said tag transmission readers are processed by an object location processor to locate a tag and thereby its object within said monitored environment, said method comprising the steps of:

(a) displaying on said computer workstation a map of said monitored environment;

(b) identifying on the map displayed in step (a) potential locations of a plurality of said tag transmission readers;

(c) generating a mathematical model of said system using said potential locations of said plurality of said tag transmission readers identified on said map in step (b);

(d) characterizing, on said map of said monitored environment, the ability of a system represented by said mathematical model generated in step (c) to identify locations of objects within said monitored environment;

measuring the geo-location performance of said system represented by said mathematical model generated in step (c) in terms of a geometric dilution of precision (gdop); and

visually characterizing gdop accuracy as an estimate of performance of the system model.

2. A method according to claim 1, wherein step (d) comprises providing coloration of said map to characterize the ability of said system represented by said mathematical model generated in step (c) to identify locations of objects within said monitored environment.

3. A method according to claim 1, further including, in response said displayed map of said monitored environment characterizing a prescribed inability of said system represented by said mathematical model generated in step (c) to identify locations of objects within said monitored environment, the step (e) of modifying said potential locations of tag transmission readers in step (b), and carrying out steps (c) and (d) based upon the modified potential locations of tag transmission readers.

4. A method according to claim 3, wherein step (e) comprises changing the potential locations of tag transmission readers in step (b), and carrying out steps (c) and (d) based upon the changed potential locations of tag transmission readers.

5. A method according to claim 3, wherein step (e) comprises changing the number of potential locations of tag transmission readers in step (b), and carrying out steps (c) and (d) based upon the changed number of potential locations of tag transmission readers.

6. A method according to claim 1, wherein step (b) includes identifying on the map displayed in step (a) one or more impairments to transmissions between tags and said plurality of spaced apart transmission readers.

7. A method according to claim 6, wherein step (b) further includes displaying the extent to which said readers are visible to various locations in said monitored environment.

8. A method according to claim 1, wherein said object location processor is operative to locate said respective tag and its associated object within said monitored environment by carrying out time-of-arrival differentiation of first-to-arrive transmissions from a respective tag as detected by said plurality of tag transmission readers.

9. A method according to claim 1, further including, in response to said displayed map of said monitored environment characterizing a prescribed ability of said system represented by said mathematical model generated in step (c) to identify locations of objects within said monitored environment, the steps of:

(e) evaluating cost of deployment of the system represented by the mathematical model generated in step (c); and

(f) selectively modifying said potential locations of tag transmission readers in step (b) in dependence upon the cost of deployment evaluation carried out in step (e), and repeating out steps (c), (d), (e) and (f) based upon the modified potential locations of tag transmission readers.

10. A method of enabling an object location system designer to specify where, relative to a monitored environment, a plurality of spaced apart tag transmission readers of said object location system for identifying locations of objects in said monitored environment are to be placed, wherein transmissions from tags coupled with said objects are to be detected at said plurality of spaced apart tag transmission readers, and outputs of said tag, transmission readers processed by an object location processor to locate a tag and associated its object within said monitored environment, said method comprising the steps of:

(a) causing a computer to display a map of said monitored environment;

(b) operating a computer input/output device to identify potential locations of tag transmission readers on said displayed map;

(c) causing said computer to measure the performance of a mathematical model of said object location system using said potential locations of tag transmission readers identified on said map in step (b);

(d) indicating, on said displayed map of said monitored environment, the ability of said object location system as represented by said mathematical model generated in step (c), to identify locations of objects within said monitored environment; and

measuring the geo-location performance of said system represented by said mathematical model in terms of a geometric dilution of precision (gdop), and wherein step (d) comprises visually characterizing gdop accuracy to which said object location system as represented by said mathematical model generated in step (c) is able to identify locations of objects within said monitored environment and estimate performance of the system.

11. A method according to claim 10, wherein step (d) comprises selectively coloring said map to visually characterize said gdop accuracy.

12. A method according to claim 10, further including, in response said displayed map of said monitored environment characterizing a prescribed inability of said system represented by said mathematical model generated in step (c) to identify locations of objects within said monitored environment, the step (e) of modifying said arrangement of potential locations of tag transmission readers in step (b), and carrying out steps (c) and (d) based upon the modified arrangement of potential locations of tag transmission readers.

13. A method according to claim 12, wherein step (e) comprises changing the potential locations and/or quantity of tag transmission readers in step (b), and carrying out steps (c) and (d) based upon the changed potential locations and/or quantity of tag transmission readers.

14. A method according to claim 10, wherein step (b) includes identifying on the map displayed in step (a) one or more impairments to transmissions between tags and said plurality of spaced apart transmission readers.

15. A method according to claim 14, wherein step (b) further includes displaying the extent to which said plurality of spaced apart transmission readers are visible to various locations in said monitored environment.

16. A system for enabling an object location system designer to place, relative to a monitored environment, a plurality of spaced apart tag transmission readers for identifying locations of objects in said monitored environment, wherein transmissions from tags coupled with said objects are to be detected at said plurality of spaced apart tag transmission readers, and outputs of said tag transmission readers processed by an object location processor to locate a tag and associated its object within said monitored environment, said system comprising:

a computer that is controllably operative to display a map of said monitored environment; and

an input/output device operation of which by said object location system designer causes said computer to display potential locations of tag transmission readers on said map; and

wherein

said computer contains a program that is operative to measure the performance of a mathematical model of said object location system using said potential locations of tag transmission readers, and to visually characterize on said displayed map of said monitored environment, the ability of said object location system as represented by said mathematical model to identify locations of objects within said monitored environment; and

wherein said program is operative to measure geo-location performance of said system represented by said mathematical model in terms of a geometric dilution of precision (gdop), and to cause said computer to visually characterize gdop accuracy to which said object location system as represented by said mathematical model generated is able to identify locations of objects within said monitored environment.

17. A system according to claim 16, wherein said program is operative to cause said computer to display the extent to which said plurality of spaced apart transmission readers are visible to various locations in said monitored environment.