Patent ID: 6453239
Filing Date: 2002-09-17
Classification: E21B,G01C

Abstract:
A strapdown inertial navigation method comprising:maneuvering a probe including at least three vibrating mass, Coriolis effect gyroscopes in a borehole; initializing the probe's attitude in the borehole within the probe's frame of reference; determining, from the gyroscopes, three orthogonal, incremental rotation angles for the probe within the probe's frame of reference; determining three orthogonal, incremental velocities for the probe within the probe's frame of reference; translating the three incremental velocities from the probe's frame of reference into the inertial frame of reference using the three incremental rotation angles; determining from the translated incremental velocities a velocity vector in a local-vertical, wander-azimuth frame of reference; obtaining a velocity error observation; estimating a system error from the velocity vector and a velocity error observation; and feeding the system error back into the inertial navigation method.