Bearing calculator and error correction method

• US 7,941,268 B2
• Filed: 10/27/2010
• Issued: 05/10/2011
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Corporation
• Inventors: Okeya, Shigeo
• Primary Examiner(s): Black; Thomas G
• Assistant Examiner(s): Chen; Shelley
• Application Number:
  US12/913,640
• Publication Number:
  US 20110045848A1
• Time in Patent Office: 195 Days
• Field of Search: 701/207
• US Class Current: 701/207
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence

Abstract

A bearing calculator provided with a geomagnetic sensor for detecting earth-geomagnetism and a control unit for calculating a geographical bearing based on detection values of the geomagnetic sensor. The control unit can execute offset error correction processing for correcting the offset error to the geomagnetic sensor based on a change in the magnetic field inside the bearing calculator. When detection values of the geomagnetic sensor enter an abnormal state, it performs said offset error correction processing when the abnormal state continues for a predetermined time, while does not perform the offset error correction processing when the abnormal state ends within a predetermined time.

Claims

1. A mobile communication terminal apparatus comprising:

a geomagnetic sensor for detecting earth-geomagnetism;

a displaying means; and

a control means for calculating a geographical bearing base on values detected by the geomagnetic sensor, and displaying the resultant bearing information on the display means, and

a position information acquisition means for acquiring information concerning a geographical position where the mobile communication terminal apparatus is positioned at this time, the control means

displaying a map of the surrounding of a current position of the mobile communication terminal apparatus which is specified on the basis of the positional information acquired by the position information acquisition means, on the display means,

displaying the bearing information included in the map on the display means, performing a control processing for controlling a direction of the map in a display screen of the display means in response to the calculated bearing, and

stopping the control processing of the direction of the bearing when the detected value of the geomagnetic sensor becomes a predetermined abnormal state and the predetermined abnormal state lasts over a predetermined time, during the execution of the control processing, and then, fixing a predetermined bearing on the map to a predetermined direction on the display screen of the display means, and correcting the bearing information.

2. A mobile communication terminal apparatus as set forth in claim 1, wherein

the geomagnetic sensor detects a plurality of earth-geomagnetism in a plurality of perpendicular directions each other,

the control means specifies an offset error of the geomagnetic sensor, when at least one of the detected values of the plurality of the earth-geomagnetism becomes the predetermined abnormal state and the predetermined abnormal state continues over a predetermined time, and corrects the bearing information by using the offset error.

3. A mobile communication terminal apparatus as set forth in claim 1, wherein the predetermined abnormal state is a state where the detected value of the geomagnetic sensor is outside a range determined as normal.

4. A mobile communication terminal apparatus as set forth in claim 1, wherein

the geomagnetic sensor converts analog signals of the earth-geomagnetism to digital signals and outputs the same as the detected value of the earth-geomagnetism, and

the predetermined abnormal state is a state where the detected value of the geomagnetic sensor is equal to a maximum value or a minimum value in the predetermined range.

5. A mobile communication terminal apparatus as set forth in claim 1, wherein the control means restarts the control of the direction of the map, when the correction processing for the bearing information has completed, after stopped the control of the direction of the map.

6. A correction method for correcting an error of a geomagnetic sensor for detecting earth-geomagnetism, used in a mobile communication terminal apparatus comprising a position information acquisition means for acquiring an information concerning a geographical position where the mobile communication terminal apparatus is positioned at this time, and a display means for displaying a geographical bearing information calculated on the basis of the detected value of the geomagnetic sensor,

the correction method including;

a first step for displaying a map of the surrounding of a current position of the mobile communication terminal apparatus which is specified on the basis of the positional information acquired by the position information acquisition means, on the display means,

a second step for displaying the bearing information included in the map on the display means,

a third step for performing a control processing for controlling a direction of the map in a display screen of the display means in response to the calculated bearing, and

stopping the control processing of the direction of the bearing when the detected value of the geomagnetic sensor becomes a predetermined abnormal state and the predetermined abnormal state lasts over a predetermined time, during the execution of the control processing, and then, fixing a predetermined bearing on the map to a predetermined direction on the display screen of the display means, and correcting the bearing information,

a fourth step for detecting the fact that the detected value of the geomagnetic sensor becomes a predetermined abnormal state under the status where the control of the direction of the map in the third step,

a fifth step for monitoring whether or not the predetermined abnormal state being continued over a predetermined time, after the detection of the predetermined abnormal state,

a sixth step for stopping the control of the direction of the map in the third step and correcting the bearing information, when the predetermined abnormal state has continued over a predetermined time, and

a seventh step for displaying a predetermined bearing on the map on the displaying means in a condition where the predetermined bearing is fixed to a predetermined direction on the display screen of the display means.

7. A correction method as set forth in claim 6, further including:

an eighth step for detecting a plurality of earth-geomagnetism in a plurality of perpendicular directions each other, by the geomagnetic sensor, and

a ninth step for specifying an offset error of the geomagnetic sensor, when at least one of the detected values of the plurality of the earth-geomagnetism becomes the

predetermined abnormal state and the predetermined abnormal state continues over a predetermined time, and corrects the bearing information by using the offset error.

8. A correction method as set forth in claim 6, wherein the predetermined abnormal state is a state where the detected value of the geomagnetic sensor is outside a range determined as normal.

9. A correction method as set forth in claim 6, further including a tenth step for converting analog signals of the earth-geomagnetism to digital signals and outputs the same as the detected value of the earth-geomagnetism, and

wherein the predetermined abnormal state is a state where the detected value of the geomagnetic sensor is equal to a maximum value or a minimum value in the predetermined range.

10. A correction method as set forth in claim 6, further including an eleventh step for restarting the control of the direction of the map, when the correction processing for the bearing information has completed, after stopped the control of the direction of the map.