Correction method for vehicle-mounted geomagnetic field sensors

Claim 2

A correction method for a geomagnetic field sensor of a bearing indication system mounted on a vehicle, said bearing indication system including signal processing means for computing and outputting a bearing of said vehicle in accordance with an output signal of said geomagnetic field sensor, said signal processing means having storing means for storing data of said bearing of said vehicle, and display means for displaying said bearing of said vehicle in accordance with an output of said signal processing means, comprising: a first step of storing said output signals of said geomagnetic field sensor as said data of said bearing of said vehicle with respect to all directions while said vehicle is traveling, said all directions being divided into at least three bearing ranges having an equal angle with each other; a second step of computing and storing a first bearing correction vector on the basis of a first set of average points each respectively determined from said data of said bearing as associated with one of all of said bearing ranges, and computing and storing a second bearing correction vector on the basis of a second set of average points each respectively determined from said data of said bearing as associated with one of at least three of said bearing ranges; and a third step of determining from the magnitude of said first correction vector whether said vehicle has traveled a geomagnetically abnormal area, and based on said determination outputting a correction signal based on either of said first or said second bearing correction vector for correcting said output signals of said geomagnetic field sensor.

Claim 3

A correction method for a geomagnetic field sensor of a bearing indication system mounted on a vehicle, said bearing indication system including signal processing means for computing and outputting a bearing of said vehicle in accordance with an output signal of said geomagnetic field sensor, said signal processing means having storing means for storing data of said bearing of said vehicle, and display means for displaying said bearing of said vehicle in accordance with an output of said signal processing means, comprising: a first step of storing said output signals of said geomagnetic field sensor as said data of said bearing of said vehicle with respect to all directions while said vehicle is traveling, said all directions being divided into at least three bearing ranges having an equal angle with each other; a second step of computing and storing an initial bearing correction vector on the basis of a set of average points each respectively determined from said data of said bearing as associated with one of all of said bearing ranges; a third step of deciding as to whether said vehicle has traveled a geomagnetically abnormal area through usage of said initial bearing correction vector and said average points each respectively determined from said data of said bearing as associated with said one of all said bearing ranges, such that when said vehicle is decided to have traveled said geomagnetically abnormal area said initial bearing correction vector is deemed to be actual, and when said vehicle is decided not to have traveled said geomagnetically abnormal area a subsequent bearing correction vector is computed on the basis of a set of average points each respectively determined from said data of said bearing as associated with one of at least three of said bearing ranges and stored in place of said initial bearing correction vector; and a fourth step of outputting a correction signal based on either of said initial bearing correction vector or said subsequent bearing correction vector as stored for correcting said output signals of said geomagnetic field sensor.

Claim 4

A correction method for a geomagnetic field sensor of a bearing indication system mounted on a vehicle, said bearing indication system including signal processing means for computing and outputting a bearing of said vehicle in accordance with an output signal of said geomagnetic field sensor, said signal processing means having storing means for storing data of said bearing of said vehicle, and display means for displaying said bearing of said vehicle in accordance with an output of said signal processing means, comprising: a first step of storing said output signals of said geomagnetic field sensor as said data of said bearing of said vehicle with respect to all directions while said vehicle is traveling, said all directions being divided into at least three bearing ranges having an equal angle with each other; a second step of computing and storing an initial bearing correction vector on the basis of a set of average points each respectively determined from said data of said bearing as associated with one of all of said bearing ranges; a third step of deciding as to whether said vehicle has traveled a geomagnetically abnormal area through usage of said initial bearing correction vector and said average points each respectively determined from said data of said bearing as associated with said one of all said bearing ranges, such that when said vehicle is decided to have traveled said geomagnetically abnormal area said initial bearing correction vector is deemed to be actual, and when said vehicle is decided not to have traveled said geomagnetically abnormal area a subsequent bearing correction vector is computed on the basis of a set of average points each respectively determined from said data of said bearing as associated with one of at least three of said bearing ranges and stored in place of said initial bearing correction vector; and a fourth step of outputting a correction signal based on either of said initial bearing correction vector or said subsequent bearing correction vector as stored for correcting said output signals of said geomagnetic field sensor.

Claim 5

A correction method according to claim 2, wherein: said geomagnetic field sensor includes detecting means for detecting a strong magnetic field; and when said detection means has detected said strong magnetic field, said data of said bearing as stored are all cleared to be zero.

Claim 6

A correction method according to claim 2, wherein: said initial bearing correction vector is updated at intervals of a predetermined period of time.

Claim 7

A correction method according to claim 2, wherein: said initial bearing correction vector is updated each time when said vehicle has traveled a predetermined distance.