Patent ID: 8622150

Claim:
In a system for tracking a boring tool which is moved in an underground region using a drill string having a length that extends to the boring tool and said boring tool having an overall orientation that is characterized by a pitch orientation, a yaw orientation and a roll orientation and which is steerable underground in the region using said roll orientation, said boring tool being configured for advancing in a straight ahead mode during a continuous roll applied by said drill string and further being configured for advancing in a steering mode by moving the boring tool at a fixed roll orientation to produce a maximum curvature in said drill string, an apparatus comprising: a drill string monitor for monitoring an advance of the boring tool over a path segment from a known, start position to an end position, where the path segment forms a portion of an overall drill path that is taken by the boring tool and includes a segment length; a sensing arrangement including a pitch sensor and a roll sensor for measuring the pitch orientation and the roll orientation of the boring tool concurrently with said monitoring of the advance of the boring tool; and a processor configured for establishing a resulting position of the boring tool at an endpoint of said path segment based on the measured pitch orientation, the measured roll orientation, the monitored advance of the drill string and the maximum curvature of the drill string.