Patent ID: 6838882
Filing Date: 2005-01-04
Classification: E21B,G01V

Abstract:
1. A method for avoiding an inground obstacle at a known depth, using a steerable boring tool which transmits a dipole locating signal, said method comprising the steps of: positioning the boring tool in a first position at a forward distance to the obstacle; measuring a signal strength of said locating signal at a location above the inground obstacle which corresponds to a field defined forward point of the locating signal such that the signal strength is representative of the depth of the boring tool at said forward distance from the obstacle; with said boring tool at said first position, determining a pitch orientation of the boring tool; determining a predicted depth of the boring tool based on at least generally straight movement of the boring tool by said forward distance toward the inground obstacle, said signal strength and said pitch orientation; and based on the predicted depth of the boring tool and the known depth of the obstacle, steering the boring tool in a way that is intended to avoid the obstacle.