Direction finder

Claim 2

An orientation finder for use on a moving vehicle, comprising: a terrestrial magnetism sensor mounted on said vehicle for detecting a pair of orthogonal components of a horizontal component of terrestrial magnetism to provide a pair of detection signals corresponding to said orthogonal components, respectively; magnetization correction means for correcting said pair of detection signals with a pair of correction values necessary to cancel out an influence of a magnetic field produced by said vehicle itself and providing a pair of corrected detection signals; and correction amending means for obtaining a perpendicular bisector of a line connecting two points corresponding to said pair of detection signals from said terrestrial magnetism sensor and said pair of corrected detection signals from said magnetization correction means on a rectangular coordinate system to amend said correction values on the basis of coordinates of a cross-point of said perpendicular bisector and a line extending perpendicularly from a point corresponding to said correction values to said perpendicular bisector.

Claim 3

The orientation finder as claimed in claim 1, wherein said correction amending means amends said correction values when a distance between coordinates corresponding to a current detection signal pair from said terrestrial magnetism sensor and a preceding detection signal pair from said terrestrial magnetism sensor stored as a reference detection signal pair becomes equal to or larger than a first predetermined value.

Claim 4

The orientation finder as claimed in claim 1 or 2, wherein said correction amending means utilizes a current detection signal pair from said terrestrial magnetism sensor as a reference detection signal pair in obtaining said perpendicular bisector when a distance between coordinates corresponding to said current detection signal pair and a detection signal pair obtained by said terrestrial magnetism sensor and stored at a predetermined time after said current detection signal pair is obtained becomes equal to or larger than a second predetermined value.

Claim 5

An orientation finder for use on a moving vehicle, comprising: a terrestrial magnetism sensor mounted on said vehicle for detecting a pair of orthogonal components of a horizontal component of terrestrial magnetism to provide a pair of electric signals corresponding to said orthogonal magnetic field components, respectively; initial correction means responsive to an output of said sensor for obtaining correction amounts; magnetization correction means for correcting said pair of electric signals with said correction amounts obtained by said initial correction means and providing a pair of corrected electric signals; correction amending means for obtaining a perpendicular bisector of a line connecting two points corresponding to said pair of detection signals from said terrestrial magnetism sensor and said pair of corrected signals from said magnetization correction means on a rectangular coordinate system to amend said correction amounts on the basis of coordinates of a cross point of said perpendicular bisector and a line extending perpendicularly from a point corresponding to said correction amounts to said perpendicular bisector; angle calculation means responsive to an output of said magnetization correction means for calculating an angle between a moving direction of said vehicle and a direction of said horizontal component of terrestrial magnetism; and display means for displaying said angle.

Claim 6

An orientation finder for use on a moving vehicle, comprising: a terrestrial magnetism sensor mounted on said vehicle for detecting a pair of orthogonal components of a horizontal component of terrestrial magnetism to provide a pair of electric signals corresponding to said orthogonal magnetic field components, respectively; initial correction means responsive to an output of said sensor for obtaining correction amounts; magnetization correction means for correcting said pair of electric signals with said correction amounts obtained by said initial correction means and providing a pair of corrected electric signals; correction amending means for obtaining a perpendicular bisector of a line connecting two points corresponding to said pair of detection signals from said terrestrial magnetism sensor and said pair of corrected signals from said magnetization correction means on a rectangular coordinate system to amend said correction amounts on the basis of coordinates of a cross point of said perpendicular bisector and a line extending perpendicularly from a point corresponding to said correction amounts to said perpendicular bisector; angle calculation means responsive to an output of said magnetization correction means for calculating an angle between a moving direction of said vehicle and a direction of said horizontal component of terrestrial magnetism; and display means for displaying said angle.

Claim 7

The orientation finder as claimed in claim 4, wherein said initial correction means, said magnetization correction means, said correction amending means and said angle calculation means constitute a control device and said control device further comprises an A/D converter connected to an output of said terrestrial magnetism sensor, a microcomputer and a display driver connected to said display means.