Static Heading Detection in Personal Navigation Device

• US 20110250931A1
• Filed: 04/01/2011
• Published: 10/13/2011
• Est. Priority Date: 04/08/2010
• Status: Active Grant

• Current Assignee: Deric Waters, Goutam Dutta, Jaiganesh Balakrishnan, Jayawardan Janardhanan, Karthik Ramasubramanian, Sandeep Rao, Sthanunathan Ramakrishnan, Tarkesh Pande
• Original Assignee: Deric Waters, Goutam Dutta, Jaiganesh Balakrishnan, Jayawardan Janardhanan, Karthik Ramasubramanian, Sandeep Rao, Sthanunathan Ramakrishnan, Tarkesh Pande
• Inventors: Ramakrishnan, Sthanunathan, Ramasubramanian, Karthik, Balakrishnan, Jaiganesh, Pande, Tarkesh, Dutta, Goutam, Waters, Deric, Rao, Sandeep, Janardhanan, Jayawardan
• Granted Patent: US 8,930,136 B2
• Time in Patent Office: Days
• US Class Current: 455/566
• CPC Class Codes: G01C 21/1654 with electromagnetic compass
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial

Abstract

A personal navigation device configured to determine heading readings continuously using data from a sensor in the personal navigation device. Heading readings are selected corresponding to a periodic event. A representative heading is determined from the selected heading readings. When a portion of the selected heading readings has a value within a range of the representative heading, a static heading indicator is asserted to indicate the personal navigation device is moving in a static heading. The static heading indicator may be used to smooth an estimated trajectory of the personal navigation device.

Claims

1. A method for navigation, the method comprising:

determining heading readings continuously using data from a sensor in a personal navigation device;

selecting heading readings corresponding to a periodic event;

determining that a portion of the selected headings have a value within a range; and

declaring the personal navigation device is moving in a static heading when the portion of the selected heading readings have a value within the range.

2. The method of claim 1, wherein determining that a portion of the selected headings have a value within the range comprises:

determining a representative heading from the selected heading readings; and

determining that a portion of the selected headings have a value within a range of the representative heading.

3. The method of claim 1, wherein determining that a portion of the selected headings have a value within the range comprises:

computing a variance of the selected heading readings; and

determining that the range of the variance is less than a threshold value.

4. The method of claim 1, further comprising

determining an estimated trajectory of the personal navigation device using data received from beacon sources;

and

smoothing the estimated trajectory using the representative heading when a static heading is declared.

5. The method of claim 1, further comprising:

receiving position data from a plurality of beacon sources;

discarding data from at least one of the beacon sources that is inconsistent with the representative heading when a static heading is declared; and

determining an estimated trajectory of the personal navigation device using remaining data received from beacon sources.

6. The method of claim 1, further comprising calibrating the sensor using the representative heading when a static heading is declared.

7. The method of claim 1, wherein the periodic event is indicative of periodic motion of the personal navigation device while a person carrying the device is walking.

8. The method of claim 1, wherein the periodic event is time based.

9. The method of claim 1, wherein the selected headings are stored in a buffer of length N.

10. The method of claim 9, wherein the buffer is emptied after each determination of the representative heading.

11. The method of claim 9, wherein the buffer is a circular buffer and a representative heading is determined each time a selected heading is stored in the buffer.

12. The method of claim 9, wherein the range is a function of N.

13. The method of claim 1, wherein the portion of the selected headings comprise odd or even headings.

14. The method of claim 1, wherein the declared static heading is a mean value of the selected headings.

15. A personal navigation device, comprising:

a sensor operable to provide heading readings indicative of motion of the personal navigation device (PND);

a processing engine coupled to receive the heading readings from the sensor, the processing engine configured to;

select heading readings corresponding to a periodic event;

determine that a portion of the selected headings have a value within a range; and

declare the personal navigation device is moving in a static heading when the portion of the selected heading readings have a value within the range.

16. The personal navigation device of claim 15, further comprising:

a second processing engine configured to determine an estimated trajectory of the personal navigation device using data received from beacon sources; and

smoothing logic coupled to receive the static heading, the smoothing logic configured to smooth the estimated trajectory using the representative heading when a static heading is declared.

17. The personal navigation device of claim 15, further comprising:

a second processing engine configured to determine an estimated trajectory of the personal navigation device using position data received from a plurality of beacon sources, wherein the second processing engine is configured to;

discard data from at least one of the beacon sources that is inconsistent with the representative heading when a static heading is declared; and

determine an estimated trajectory of the personal navigation device using remaining data received from beacon sources.

18. The personal navigation device of claim 15, wherein the processing engine is configured to determine a periodic event correlated to periodic motion of the PND resulting from steps being taken by a user while carrying the PND.

19. The personal navigation device of claim 15, wherein the processing engine is further operable to store the selected heading readings in a buffer of length N;

and wherein the range is a function of N.

20. The personal navigation device of claim 15, further comprising:

a display screen operable to display the estimated trajectory of the PND; and

a radio transceiver with data processing logic coupled to the display screen, the transceiver operable to send and receive cellular telephone voice and data streams via a cellular network.