| 主权项 |
1. In a system including a steering tool that is moved by a drill string and steered in a way that is intended to form an underground bore along an intended path, beginning from a starting position, an apparatus comprising:
a sensing arrangement, forming one part of the steering tool, for detecting a pitch orientation and a yaw orientation of the steering tool at each of a series of spaced apart positions of the steering tool along said underground bore, each of which spaced apart positions is characterized by a measured extension of said drill string such that each of the detected pitch orientation and yaw orientation are subject to a measurement error; at least one marker positioned proximate to the intended path, for transmitting a rotating dipole field such that a portion of the intended path is exposed to the rotating dipole field; a receiver, forming another part of the steering tool, configured for receiving the rotating dipole field to produce magnetic information; and a processor that is configured (i) for operation in a first mode using the detected pitch orientation, the detected yaw orientation and a measured extension of the drill string at one of the spaced apart positions that is not exposed to the rotating dipole field to determine one position of the steering tool with a given accuracy, relative to a last-determined position as part of the series of spaced apart positions, subject to the measurement error, and (ii) for operation in a second mode using the magnetic information in conjunction with the detected pitch orientation, the detected yaw orientation and the measured extension of the drill string to determine another position of the steering tool at another one of the spaced apart positions along said portion of the intended path that is exposed to the rotating dipole field, relative to the last-determined position in the series of spaced apart positions, with an enhanced accuracy, as compared to the given accuracy, to compensate for the accumulation of the measurement error. |
