Geo-fence with minimal false alarms

• US 8,125,332 B2
• Filed: 11/21/2008
• Issued: 02/28/2012
• Est. Priority Date: 11/21/2008
• Status: Active Grant

• Current Assignee: Freeus, LLC
• Original Assignee: Zoombak LLC (Kratos Defense & Security Solutions Incorporated)
• Inventors: Curran, David, Fanshier, Rand A., Demmel, Jesse
• Primary Examiner(s): BLOUNT, ERIC
• Application Number:
  US12/276,246
• Publication Number:
  US 20100127919A1
• Time in Patent Office: 1,194 Days
• Field of Search: 3405391-53913, 340/572.1, 340988-996, 342/350, 342/357.22, 342/357.25, 342450-465, 455/456.1, 455/456.3
• US Class Current: 340/539.13
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: H04W 4/021 Services related to particular areas, e.g. point of interest [POI] services, venue services or geofences

Abstract

A method and apparatus is disclosed for a wireless device locator system and determining whether a device has entered or exited a two dimensional geographic zone area and alerting the device user when the device has entered or exited the zone. The method and apparatus may further minimize the probability of false zone entry and exit zone area alerts to wireless tracking device users.

Claims

1. A method of tracking movement of a wireless location device relative to a predefined geographic boundary, comprising:

receiving a position fix and error data defining an error zone around the position fix;

determining a distance between the position fix and a zone boundary edge;

determining a zone alert confidence threshold as a function of the distance between the position fix and the zone boundary edge, the geographic boundary circle radius, and the error data;

determining that the zone alert confidence threshold meets a predefined level; and

providing notification that the device has crossed the predefined geographical boundary.

2. The method of claim 1, wherein said predefined level comprises at least a first level indicating that the device has crossed the predefined geographical boundary, a second level indicating that the device may have crossed the predefined geographical boundary, a third level indicating that the device is in proximity to but has not crossed the predefined geographical boundary, or a fourth level indicating that the device has not crossed the predefined geographical boundary.

3. The method of claim 2, further comprising notifying a location server of a state change when said confidence threshold is at the first level.

4. The method of claim 3, further comprising notifying a location server of a state change when said confidence threshold is at the third level.

5. The method of claim 3, wherein the location server is notified only when a user configuration indicates that the location server should be notified, further comprising storing the state when a previous level is unknown.

6. The method of claim 2, further comprising determining a device location based on two consecutive location fixes when the zone alert confidence threshold is at the second level.

7. The method of claim 2, further comprising determining a need for notification upon exit from a geo-fenced area based on two consecutive location fixes when the confidence threshold is at the third level.

8. The method of claim 2, wherein said determining a zone alert confidence threshold is performed according to a polling interval.

9. The method of claim 8, further comprising decreasing the polling interval when the confidence threshold transitions to level 1.

10. The method of claim 8, further comprising increasing the polling interval when the confidence threshold transitions from level 1 to any other level.

11. The method of claim 8, further comprising using a predetermined polling interval.

12. The method of claim 1, further comprising:

determining a location uncertainty upper limit as a ratio of a horizontal uncertainty and the geographic boundary circle radius; and

discarding a position fix when the location uncertainty upper limit meets a predetermined level.

13. The method of claim 1, wherein said determining a zone alert confidence threshold is performed according to a zone alert schedule, the schedule comprising a range of dates and times for determining when the device has entered or exited the predefined geographic boundary.

14. The method of claim 1, wherein said position fix comprises a latitude, a longitude, and an error uncertainty ellipse comprising a major axis radius and minor axis radius.

15. The method of claim 1, wherein said wireless location device implements at least one of GPS, U-TDOA, E-OTD, or ECID positioning technologies.

16. A method of tracking movement of a wireless location device relative to a predefined geographic boundary, comprising:

receiving indication that the wireless location device has crossed the predefined geographical boundary;

receiving from the device at least two consecutive measurements of positioning data and associated positioning data accuracies;

determining that the positioning data accuracies meet a predefined level; and

providing notification that the device has crossed the predefined geographical boundary when the positioning data accuracies meet the predefined level.

17. A computing system adapted to track movement of a wireless location device relative to a predefined geographical boundary, comprising:

a server; and

computing memory communicatively coupled to said server, the computing memory having stored therein a software application adapted to perform the following;

define a two dimensional geographic zone area corresponding to said predefined geographical boundary;

implement a timer for periodically commanding at least one positioning wireless location device to wake up from a sleep mode;

request a position fix from said at least one wireless location device when the device reports an accuracy that meets an accuracy threshold; and

wirelessly send an alert when the device has crossed the predefined geographical boundary.

18. The system of claim 17, further adapted to send to said at least one wireless location device a text message comprising at least one instruction command instructing the device to:

establish a wireless data session with the server;

request specific data from the server related to the at least one instruction command, and

process and store the received specific data on the device.

19. The system of claim 17, further adapted to receive a position fix log from the at least one positioning wireless location device and transmit contents of said position fix log to a web server for retrieval by a user.

20. A wireless location determination device for tracking movement relative to a predefined geographic boundary, the device configured to:

periodically request a position fix and associated position fix error based on a predetermined timer value; and

transmit an alert via a wireless network when the device has crossed the predefined geographic boundary.

21. The device of claim 20, further configured to detach from the wireless network, power off at least one device module, and terminate at least one software process based on predefined software logic.

22. The device of claim 20, further configured to:

store position fixes on the device;

periodically establish a wireless data session with a server and send the stored position fixes to the server.