Development and field testing of a RLG strapdown inertial survey system

The authors describe the successful modification of a ring laser gyro (RLG) strapdown inertial reference unit into a strapdown inertial survey system (SISS) for geodetic positioning. The system, a Litton LTN-90-100, has been modified into a land-vehicle mode inertial survey system by developing specialized software and error control techniques. The software package integrates the raw body rate and acceleration data from the LTN-90-100 into velocity and coordinates of the system. The error states of the SISS are estimated by a Kalman filter-smoother using regular zero velocity measurements and occasional control coordinates as updates. The system was tested on an L-shaped baseline near Calgary and results show that a positioning accuracy of better than 1 m (1σ) is achievable