Continuous measurement for fiber optic gyro inclinometer with motion constraint

A novel continuous borehole surveying scheme for fiber optic gyro inclinometer was proposed to improve the measurement accuracy and efficiency. Virtual velocity measurements were derived from motion constraints, and utilized with cable velocity measurements as external aiding sources when cable velocity was available. However when cable velocity measurements were unavailable, only virtual velocity measurements were used as aiding sources. An indirect feedback Kalman filter was designed to limit inertial navigation errors, and thus continuous measurement operations could be performed. Field Experiments show that the inclination error is less than 0.1°, and the azimuth error is less than 1° when cable velocity is available. Meanwhile, during 5 min distortion of cable velocity, the relative azimuth and inclination error can be limited within 0.5° and 0.02° with motion constraints. Therefore, the feasibility and effectiveness of the proposed scheme was validated and evaluated.