Dual-calibrated compass

A method for calibrating a vehicle compass system to account for changes in vehicular magnetism, the vehicle compass system having a magnetic field sensor for providing electrical signals representing the earth's magnetic field, a processing circuit for processing said electrical signals to generate vehicle heading signals representing the vehicle's heading, and a heading indicator indicating the vehicle's heading in response to the vehicle heading signals received from the processing circuit, said method comprising the steps of:

• (a) calculating a vehicle heading in response to the electrical signals output from the magnetic field sensor using precalibration data to compensate for expected vehicular magnetism;
• (b) generating and supplying a vehicle heading signal representing the vehicle heading calculated in step (a) to the heading indicator;
• (c) executing an automatic calibration routine to calculate compensation data to correct for actual vehicular magnetism and to calculate a vehicle heading in response to said received electrical signals using the compensation data;
• (d) determining whether the automatic calibration routine has acquired sufficient data from said magnetic field sensor to calibrate the compass system;
• (e) repeating steps (a) through (d) until it has been determined in step (d) that the automatic calibration routine has acquired sufficient data;
• and
• (f) generating and supplying vehicle heading signals to the heading indicator representing vehicle headings calculated in response to said received electrical signals using the compensation data generated by the automatic calibration routine.

A method for calibrating a vehicle compass system to account for changes in vehicular magnetism, the vehicle compass system having a magnetic field sensor for providing electrical signals representing the earth's magnetic field, a processing circuit for processing said electrical signals to generate vehicle heading signals representing the vehicle's heading, and a heading indicator indicating the vehicle's heading in response to the vehicle heading signals received from the processing circuit, said method comprising the steps of:

• (a) calculating a vehicle heading in response to the electrical signals output from the magnetic field sensor using precalibration data to compensate for expected vehicular magnetism;
• (b) generating and supplying a vehicle heading signal representing the vehicle heading calculated in step (a) to the heading indictor;
• (c) executing an automatic calibration routine to calculate compensation data to correct for actual vehicular magnetism and to calculate a vehicle heading in response to said received electrical signals using the compensation data;
• (d) determining whether the automatic calibration routine has acquired sufficient data from said magnetic field sensor to calibrate the compass system;
• (e) determining whether the vehicle heading calculated in step (a) is the same as the vehicle heading calculated in step (c);
• (f) repeating steps (a) through (e) until (1) it has been determined in step (d) that the automatic calibration routine has acquired sufficient data and (2) it has been determined in step (e) that the vehicle heading calculated in step (a) is the same as the vehicle heading calculated in step (c);
• and
• (g) generating and supplying vehicle heading signals to the heading indicator representing vehicle headings calculated in response to said received electrical signals using the compensation data generated by the automatic calibration routine.

An electronic compass system for a vehicle comprising:

• a magnetic field sensor for detecting the earth's magnetic field and for providing electrical signals representing the direction of the vehicle in relation to the earth's magnetic field;
• a heading indicator for indicating vehicle headings in response to received vehicle heading signals;
• and
• a processor coupled to said magnetic field sensor for receiving said electrical signals and coupled to said heading indicator for supplying the vehicle heading signals to said heading indicator, said processor including
• first compass control means for calculating vehicle headings in response to said received electrical signals using precalibration data to compensate for expected vehicular magnetism,
• second compass control means for calculating vehicle headings in response to said received electrical signals using an automatic calibration routine to compensate for actual vehicular magnetism, and
• control transfer means for initially selecting the vehicle headings calculated by said first compass control means to be represented by the vehicle heading signals supplied to said heading indicator, and for selecting the vehicle headings calculated by said second compass control means when a vehicle heading calculated by said first compass control means is the same as a vehicle heading calculated by said second compass control means.

An electronic compass system for a vehicle comprising:

• a magnetic field sensor for detecting the earth's magnetic field and for providing electrical signals representing the direction of the vehicle in relation to the earth's magnetic field;
• a memory for storing a plurality of prestored audio messages each corresponding to a different vehicle heading;
• a processor coupled to said magnetic field sensor for receiving said electrical signals and calculating a vehicle heading in response to said electrical signals, said processor further being coupled to said memory for selecting for playback one of said plurality of prestored audio messages that corresponds to the calculated vehicle heading;
• a first compass control means for calculating vehicle headings in response to said electrical signals using precalibration data to compensate for expected vehicular magnetism,
• a second compass control means for calculating vehicle headings in response to said electrical signals using an automatic calibration routine to compensate for actual vehicular magnetism;
• and
• a control transfer means for initially selecting the vehicle headings calculated by said first compass control means to be represented by the vehicle heading signal supplied to said heading indicator, and for selecting the vehicle headings calculated by said second compass control means after the automatic calibration routine has acquired sufficient data from said magnetic field sensor to calibrate the compass system;
• and
• an audio transducer coupled to said processor and said memory means for audibly generating the selected prestored audio message.

An accessory for a vehicle comprising:

• a housing;
• an electronic compass field for providing electrical signals representing the direction of the vehicle in relation to the earth's magetic field, provided in said housing for indicating the vehicle's heading;
• an audio input means provided in said housing for receiving an audible message;
• a memory coupled to said audio input means for storing audio messages;
• a transducer provided in said housing and coupled to said memory for audibly generating a selected audio message;
• a user interface provided in said housing for receiving user commands;
• and
• a processor coupled to said user interface, said transducer, said audio input means, and said memory, wherein said processor responds to a record command received from said user interface by enabling said audio input means to digitize a received audible message and by recording the digitized message in said memory, and said processor responds to a playback command received from said user interface by selecting and reading a recorded audio message from said memory and by enabling said transducer to audiblize the recorded audio message;
• and
• a first compass control means for calculating vehicle headings in response to said electrical signals using precalibration data to compensate for expected vehicular magnetism
• a second compass control means for calculating vehicle headings in response to said electrical signals using an automatic calibration routine to compensate for actual vehicular magnetism;
• and
• a control transfer means for initially selecting the vehicle headings calculated by said first compass control means to be represented by the vehicle heading signal supplied to said heading indicator, and for selecting the vehicle headings calculated by said second compass control means after the automatic calibration routine has acquired sufficient data from said magnetic field.