Patent ID: 7076342

Claim:
An attitude sensing apparatus having a GPS attitude sensing system which determines the attitude of a mobile unit in an antenna coordinate system and an IMU attitude sensing system which determines the attitude of the mobile unit in an IMU coordinate system, and further determining the attitude of the mobile unit by integrating the attitudes of the mobile unit determined in the antenna coordinate system and the IMU system, said attitude sensing apparatus comprising: an alignment angle estimator for successively estimating an alignment angle to be used in a succeeding calculation process based on the difference between GPS data calculated from observations by said GPS attitude sensing system and inertia data observed by said IMU attitude sensing system; and an alignment angle adder for generating an updated alignment angle by cumulatively adding the successively estimated alignment angle and thereby sequentially updating the estimated alignment angle and for outputting the updated alignment angle to said alignment angle estimator; wherein the estimated alignment angle is successively fed back for use in the alignment angle estimation process.