Geofence with Kalman filter

• US 9,420,421 B2
• Filed: 06/26/2015
• Issued: 08/16/2016
• Est. Priority Date: 06/12/2012
• Status: Active Grant

• Current Assignee: TeleCommunication Systems Inc (Comtech Telecommunications Corporation)
• Original Assignee: TeleCommunication Systems Inc (Comtech Telecommunications Corporation)
• Inventors: Qiu, Weigen
• Primary Examiner(s): RAMPURIA, SHARAD K
• Application Number:
  US14/752,009
• Publication Number:
  US 20150319570A1
• Time in Patent Office: 417 Days
• Field of Search: 4554561-457
• US Class Current: 1/1
• CPC Class Codes: G01S 19/42 Determining position
• CPC Class Codes: G01S 5/0268 by deriving positions from different combinations of signals or of estimated positions in a single positioning system
• CPC Class Codes: G01S 5/0294 Trajectory determination or predictive filtering, e.g. target tracking or Kalman filtering
• CPC Class Codes: H04W 4/021 Services related to particular areas, e.g. point of interest [POI] services, venue services or geofences
• CPC Class Codes: H04W 4/027 using movement velocity, acceleration information
• CPC Class Codes: H04W 4/029 Location-based management or tracking services
• CPC Class Codes: H04W 52/02 Power saving arrangements in wired systems H04L12/12; signaling of mobile application services, e.g. low battery notifications H04W4/20
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A least squares geofence method that minimizes trigger misfires caused by data variability and location blunders and minimizes delayed/missed entry triggers generated under urban or indoor conditions. The least squares geofence method uses a weighted least squares (LS) model to compute a location estimate for a target device. A LS location estimate is used to determine if a target device is located inside or outside a predefined geofence. The present invention additionally comprises a Kalman filter geofence method that further improves the accuracy of entry/exit geofence triggers. A Kalman filter geofence method uses a Kalman filter to filter location data retrieved for a target device. Filtered location data is used to determine if a target device is located inside or outside a predefined geofence. A Kalman filter geofence method estimates velocity and heading information for a target device to generate accurate entry/exit geofence triggers for devices in fast moving mode.

Claims

1. A method of detecting a geofence crossing, comprising:

a Kalman filter module to filter a plurality of past individual location fixes retrieved for a wireless device and produce a latest Kalman-filtered location of said wireless device;

triggering a geofence boundary crossing by said wireless device based on said latest Kalman-filtered location of said wireless device, on a predictive heading and velocity, and on a given geofence having said boundary; and

dynamically determining a time interval before a subsequent Kalman-filtered location of said wireless device, said time interval being determined based on a velocity of said wireless device.

2. The method of detecting a geofence crossing according to claim 1, further comprising:

detecting a location blunder of said latest Kalman-filtered location of said wireless device using said latest Kalman-filtered location.

3. The method of detecting a geofence crossing according to claim 1, further comprising:

dynamically determining an appropriate number of individual location fixes retrieved for said wireless device to produce said subsequent Kalman-filtered location of said wireless device.

4. The method of detecting a geofence crossing according to claim 1, further comprising:

dynamically selecting an energy efficient method of obtaining a current location of said wireless device based both on said latest Kalman-filtered location, and on said predictive heading and velocity of said wireless device relative to said given geofence.

5. The method of detecting a geofence crossing according to claim 1, wherein:

said given geofence is moving.

6. The method of detecting a geofence crossing according to claim 1, further comprising:

reducing a time interval between successive location fixes for said wireless device when said latest Kalman-filtered location is outside said given geofence.

7. The method of detecting a geofence crossing according to claim 1, further comprising:

creating a trip profile for said wireless device based on historical measurements of said predictive heading and velocity of said wireless device.

8. A method of detecting a geofence crossing, comprising:

a Kalman filter module to filter a plurality of past individual location fixes retrieved for a wireless device and produce a latest Kalman-filtered location of said wireless device;

triggering a geofence boundary crossing by said wireless device based on said latest Kalman-filtered location of said wireless device, on a predictive heading and velocity, and on a given geofence having said boundary; and

dynamically determining an appropriate number of individual location fixes retrieved for said wireless device to produce a subsequent Kalman-filtered location of said wireless device, based on a velocity of said wireless device.

9. The method of detecting a geofence crossing according to claim 8, further comprising:

detecting a location blunder of said latest Kalman-filtered location of said wireless device using said latest Kalman-filtered location.

10. The method of detecting a geofence crossing according to claim 8, further comprising:

dynamically selecting an energy efficient method of obtaining a current location of said wireless device based both on said latest Kalman-filtered location, and on a predictive heading and velocity of said wireless device relative to said given geofence.

11. The method of detecting a geofence crossing according to claim 8, wherein:

said given geofence is moving.

12. The method of detecting a geofence crossing according to claim 8, further comprising:

reducing a time interval between successive location fixes for said wireless device when said latest Kalman-filtered location is outside said given geofence.

13. The method of detecting a geofence crossing according to claim 8, further comprising:

creating a trip profile for said wireless device based on historical measurements of said predictive heading and velocity of said wireless device.