Loran compensated magnetic compass

• US 4,024,382 A
• Filed: 09/08/1975
• Issued: 05/17/1977
• Est. Priority Date: 09/08/1975
• Status: Expired due to Term

• Current Assignee: Laitram LLC
• Original Assignee: Laitram LLC
• Inventors: Fowler, John T.
• Primary Examiner(s): Morrison, Malcolm A.
• Assistant Examiner(s): Krass, Errol A.
• Application Number:
  US05/611,525
• Time in Patent Office: 617 Days
• Field of Search: 235/150.26, 235/151.3, 235/150.27, 235/150.25, 235/150.53, 340/347 DD, 33/317 D, 33/317 R, 33/319, 33/325, 33/326, 33/356, 33/363 R, 318/580, 343/114
• US Class Current: 701/207
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

A magnetic compass system in which an output signal indication is produced of true heading. An electronic navigation receiver such as a Loran or Omega receiver is employed to provide sequential indications of present position which are processed to produce a signal representing the average course made good for a selected heading. The course made good signal is processed with a signal indication of magnetic compass heading to correct for deviation and variation errors and yield an output signal representing true heading.

Claims

1. A magnetic compass system comprising:

a magnetic compass providing an output signal representative of magnetic compass heading;

an electronic navigation receiver providing an output signal representative of present position;

means responsive to at least two sequential readings from said navigation receiver to provide an output representative of average course made good for a selected heading;

an averaging circuit responsive to the output signal from said magnetic compass to provide a signal representative of average magnetic compass heading;

first subtracting means receiving said signal representative of average course made good and said signal representative of average compass heading and providing an output signal representative of average error therebetween; and

second subtracting means receiving said signal representative of average error and signal representative of magnetic compass heading and providing an output signal representative of true heading.

2. A magnetic compass system according to claim 1 wherein said first subtracting means includes:

means for storing a representation of said average error.

3. A magnetic compass system according to claim 2 further including:

a second averaging circuit operative in response to said output signal representative of true heading to provide an output signal representative of average true heading.

4. A magnetic compass system according to claim 1 wherein said averaging circuit has a time constant small compared to intended turning movements of a vessel aboard which the system is employed.

5. A magnetic compass system comprising:

a digital magnetic compass providing a digital output signal representative of magnetic heading;

means operative in response to output signals from an electronic navigation receiver representative of present position to provide a digital output representative of average course made good for a selected heading;

an averaging circuit operative in response to the output signal from said magnetic compass to provide a digital signal representative of average magnetic heading;

circuit means operative in response to said signal representative of average course made good and said signal representative of average heading to provide a digital signal representative of average error between said average course made good and average magnetic heading; and

circuit means operative in response to said average error signal and magnetic compass output signal to provide a digital output signal representative of true heading.

6. For use with a remote reading magnetic compass providing an output signal indication of magnetic compass heading, a method of compensating the compass output signal to correct magnetic errors, said method comprising the steps of:

providing an electrical output signal representative of magnetic compass heading;

providing a first electrical signal representative of average course made good for a selected heading;

providing a second electrical signal representative of average magnetic compass heading;

combining said first and second electrical signals to provide a third signal representative of average error therebetween; and

combining said output signal and said third signal to provide a compensated output signal representative of true heading.

7. A method according to claim 6 further including the step of averaging said compensated output signal to provide an output signal representative of average true heading.