Apparatus for generating a heading signal for a land vehicle

Claim 3

The apparatus of Claim 1, wherein: said plurality of independent direction signals respectively include errors having essentially independent spectral characteristics; and said processing means includes means for selectively filtering at least one direction signal of said plurality of independent direction signals according to the spectral characteristics of the errors included in said at least one direction signal.

Claim 4

The apparatus of Claim 1, wherein: said plurality of independent direction signals respectively include errors having essentially independent spectral characteristics, and said processing means includes means for selectively filtering a combination of said plurality of independent direction signals according to the spectral characteristics of the errors of at least one of said plurality of independent directions signals.

Claim 5

The apparatus of Claim 1, wherein said plurality of said independent direction signals include errors and said processing means includes: filter means for reducing the effects of the errors.

Claim 6

The apparatus of Claim 1, wherein said plurality of said independent direction signals include errors and said processing means includes: filter means, responsive to a filter control signal, for reducing the effects of said errors; and means for generating said filter control signal in response to a parameter indicating the estimated error magnitude of at least one of said plurality of direction signals at a given time.

Claim 7

The apparatus of Claim 1, wherein said plurality of independent direction signals include errors and said processing means includes: filter means, responsive to a filter control signal, for reducing the effects of said errors; and means for generating said filter control signal in response to a parameter indicating the estimated error magnitude of a combination of at least two of said plurality of direction signals at a given time.

Claim 8

An apparatus of Claim 1, wherein said plurality of independent direction signals include errors and said processing means includes: filter means, responsive to a filter control signal, for reducing the effects of said errors; and means for generating said filter control signal in response to a plurality of parameters indicating the reliability of said second sensor means, said first sensor means, and the combination of said first sensor means and said second sensor means.

Claim 9

The apparatus of Claim 1, wherein: said plurality of independent direction signals include at least a first direction signal and a second direction signal; said first direction signal including errors having primarily first spectral characteristics; said second direction signal including errors having primarily second spectral characteristics that are different from said first spectral characteristics; and wherein said processing means includes first means for combining said first direction signal and said second direction signal to generate a combined error signal essentially isolating said first and second errors from said heading information; filter means for filtering said combined error signal according to filter characteristics approximating said first spectral characteristics to generate a filtered error signal including essentially said second errors; and second means for combining said filtered error signal and said second direction signal to offset said second errors and thereby provide an improved estimate of said heading information.

Claim 10

The apparatus of Claim 8, wherein said filter means includes means, responsive to a filter control signal, for varying said filter characteristics; and means for generating said filter control signal in response to said first direction signal and said second direction signal.

Claim 13

The apparatus of Claim 10, wherein said absolute direction signal includes errors and said processing means includes: means for reducing the effects of errors in said absolute direction signal.

Claim 14

The apparatus of Claim 10, wherein said relative direction signal includes errors and said processing means includes: means for reducing the effects of errors in said relative direction signal.

Claim 15

The apparatus of Claim 10, wherein said absolute direction signal and relative direction signal include errors and said processing means includes: filter means, responsive to a filter control signal, for filtering at least a portion of said errors from said absolute direction signal and said relative direction signal; and means for generating said filter control signal in response to a parameter indicating the estimated error magnitude of errors in at least one of said absolute direction signal and said relative direction signal at a given time.

Claim 16

The apparatus of Claim 10, wherein said absolute direction signal and relative direction signal include errors and said processing means includes: filter means, responsive to a filter control signal, for filtering at least a portion of said errors from said absolute direction signal and relative direction signal; and means for generating said filter control signal in response to a parameter indicating the estimated error magnitude of a combination of said relative direction signal and said absolute direction signal at a given time.

Claim 17

The apparatus of Claim 10, wherein said absolute direction signal and relative direction signal include errors and said processing means includes: filter means, responsive to a filter control signal, for filtering high frequency errors from said direction signals; and means for generating said filter control signal in response to a plurality of parameters indicating the reliability of said second sensor means and said first sensor means.

Claim 18

The apparatus of Claim 10, wherein said second sensor means comprises: compass means for generating a compass signal indicating the heading of the land vehicle relative to the magnetic field of the earth.

Claim 19

The apparatus of Claim 13, wherein said second sensor means comprises: compass means for generating a compass signal indicating the heading of the land vehicle relative to the magnetic field of the earth; and further including means for generating said parameter by detecting fluctuations in a magnitude component of said compass signal relative to the expected magnitude of the magnetic field of the earth.

Claim 20

The apparatus of Claim 17, wherein said means for generating said parameter includes: leans for receiving the magnitude component of the compass signal generated by said compass means; means for storing a table of expected magnitudes of the magnetic field of the earth for a set of directions; means for comparing the magnitude component of the compass signal generated by said compass means with the expected magnitude of the magnetic field of the earth from said table to generate a difference signal; and means responsive to said difference signal to generate said parameter.

Claim 21

The apparatus of Claim 14, wherein said second sensor means comprises: compass means for generating a compass signal having a directional component indicating the heading of the land vehicle; and wherein said means for generating said one parameter includes means for combining said relative direction signal and the directional component of said compass signal to generate a combined error signal; and means for generating a ' deviation signal indicating statistical deviation of said combined error signal; and means responsive to said deviation signal to generate said one parameter.

Claim 22

The apparatus of Claim 10, wherein said processing means includes: first means for combining said relative direction signal and said absolute direction signal to generate a combined error signal indicating the difference between said relative direction signal and said absolute direction signal; filter means for filtering relatively high frequency errors from said combined error signal to generate a filtered error signal; and second means for combining said filtered error signal and said relative direction signal to generate the improved estimate of the heading of the land vehicle.

Claim 23

The apparatus of Claim 10, wherein said first sensor means comprises: differential odometer sensor means for generating said relative direction signal.

Claim 24

The apparatus of Claim 13, wherein said first sensor means comprises: differential odometer sensor means for generating said relative direction signal; and further including means for generating said parameter by measuring the velocity and ratio of turn of said vehicle.

Claim 25

The apparatus of Claim 10, wherein said second sensor means comprises: compass means for generating compass heading data indicating the heading of the land vehicle relative to the direction of the magnetic field of the earth; means for providing a map data base including map heading data indicating the heading of a land vehicle on a particular street for streets in a given area; selector means, responsive to a selection signal, for selecting said compass heading data or said map heading data as said absolute direction signal; and selector control means for supplying said selection signal.

Claim 26

The apparatus of Claim 23, wherein said selector control means is responsive to at least one parameter, and further including: means supplying said at least one parameter.

Claim 27

The apparatus of Claim 24, wherein said means for supplying said at least one parameter includes: means for generating one parameter for selection of said map heading data when the estimated heading of the land vehicle is within a threshold of said map heading data.

Claim 28

The apparatus of Claim 24, wherein said means for supplying said at least one parameter includes: means for determining whether the land vehicle is traveling on a particular street; and means for supplying one parameter for selection of said map heading data when the vehicle is located on the particular street.

Claim 29

The apparatus of Claim 24, wherein said means for supplying said at least one parameter includes: means for storing data identifying geographic locations on the map having characteristics which cause said compass means to be unreliable; and means for supplying one parameter for selection of said map heading data when the vehicle is located within one of said geographic locations.

Claim 30

The apparatus of Claim 23, further including: a vehicle navigation system for locating the land vehicle; and said selection signal is supplied to said vehicle navigation system as a parameter used in locating the land vehicle.

Claim 31

In a vehicle navigation system for automatically tracking a motor vehicle moveable over a given area identified by a map, an apparatus for generating data regarding the heading of the motor vehicle, comprising: first sensor means for generating a relative direction signal including heading information indicating a heading direction of the motor vehicle relative to a prior heading of the motor vehicle and including first errors ; second sensor means for generating an absolute direction signal including heading information indicating a heading direction for the motor vehicle relative to the earth and including second errors, said second sensor means including compass means for generating compass heading data indicating the heading of the motor vehicle relative to the earth, means for providing a map data base including map heading data indicating the heading of a motor vehicle on a particular street for streets in the given area, selector means, responsive to a selector control signal, for selecting said compass heading data or said map heading data as said absolute direction signal, and means supplying said selector control signal; first combining means for subtracting said relative direction signal from said absolute direction signal to generate a combined error signal; filter means, responsive to a filter control signal, for filtering said combined error signal to essentially cancel said second errors and generate a filtered error signal, said filter means including means for generating said filter control signal in response to at least one parameter indicating the estimated magnitude of error of at least one of said first and second sensor means at a given time; and second combining means for adding said filtered error signal to said relative direction signal to essentially cancel said first errors in said relative direction signal to generate an improved estimate of the heading of the motor vehicle.

Claim 32

In a vehicle navigation system for automatically tracking a motor vehicle moveable over a given area identified by a map, an apparatus for generating data regarding the heading of the motor vehicle, comprising: first sensor means for generating a relative direction signal including heading information indicating a heading direction of the motor vehicle relative to a prior heading of the motor vehicle and including first errors ; second sensor means for generating an absolute direction signal including heading information indicating a heading direction for the motor vehicle relative to the earth and including second errors, said second sensor means including compass means for generating compass heading data indicating the heading of the motor vehicle relative to the earth, means for providing a map data base including map heading data indicating the heading of a motor vehicle on a particular street for streets in the given area, selector means, responsive to a selector control signal, for selecting said compass heading data or said map heading data as said absolute direction signal, and means supplying said selector control signal; first combining means for subtracting said relative direction signal from said absolute direction signal to generate a combined error signal; filter means, responsive to a filter control signal, for filtering said combined error signal to essentially cancel said second errors and generate a filtered error signal, said filter means including means for generating said filter control signal in response to at least one parameter indicating the estimated magnitude of error of at least one of said first and second sensor means at a given time; and second combining means for adding said filtered error signal to said relative direction signal to essentially cancel said first errors in said relative direction signal to generate an improved estimate of the heading of the motor vehicle.