Azimuth/attitude detecting sensor

The sensor successively calculates a rolling angle, pitch angle and azimuth from the coordinate transformation matrix with the level error and azimuth error compensated. It calculates (26) azimuth error compensatory values 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 azimuth error compensatory values using the 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 not low.