Azimuth/attitude detecting sensor

An azimuth/attitude detecting sensor mounted on a mobile unit for detecting an azimuth/attitude of the mobile unit, comprising:

• at least three gyros that detect angular velocities around three axes and output angular velocity signals;
• at least three accelerometers that detect accelerations in three axial directions and output acceleration signal;
• GPS receiver that detects a moving direction of the mobile unit using GPS and outputs GPS direction signal;
• a magnetic azimuth sensor that detects the magnetic azimuth and outputs magnetic azimuth signal;
• and
• calculation unit for receiving the angular velocity signals output from the gyros, the acceleration signals output from the accelerometers, the GPS direction signal output from the GPS receiver, the magnetic azimuth signal output from the magnetic azimuth sensor and calculating a rolling angle, pitch angle and azimuth,
• wherein said calculation unit comprises:
• a coordinate transformation matrix updating section that successively calculates and updates a coordinate transformation matrix from a body coordinate system to which the gyros and accelerometers are attached, into a local coordinate system using said angular velocity signals;
• a coordinate transformation section that performs a coordinate transformation of said acceleration signals using the coordinate transformation matrix from said coordinate transformation matrix updating section;
• a calculation section for level error compensatory value that calculates a level error compensatory value using the acceleration signals transformed by the coordinate transformation section;
• a calculation section for azimuth error compensatory value that calculates an azimuth error compensatory value using the GPS direction signal and magnetic azimuth signal;
• an attitude/azimuth calculation section that calculates a rolling angle, pitch angle and azimuth from said coordinate transformation matrix compensated by the level error compensatory value and azimuth error compensatory value, and
• said calculation section for azimuth error compensatory value calculates the azimuth error compensatory value using the GPS direction signal and calculates a difference between the GPS direction signal and magnetic azimuth signal under a condition wherein the reliability of the GPS direction signal is high, whereas it calculates the azimuth error compensatory value using said calculated difference between the GPS direction signal and magnetic azimuth signal and the magnetic azimuth signal under a condition wherein the reliability of the GPS direction signal is not high and under a condition wherein the reliability of the magnetic azimuth signal is high.