Patent ID: 6954073

Claim:
In a system in which an inground device is moved through the ground within a region along a path, an apparatus for establishing a location of at least a portion of said path, said apparatus comprising: a portable locator; an information generating arrangement for generating certain information including a set of positional information characterizing an inground position of the inground device relative to a locating position of the portable locator in said region, said information generating arrangement being located partially at and forming part of said inground device and partially at and forming part of said portable locator, and said information generating arrangement including a transmitter for transmitting a dipole field from the inground device and a receiver including less than five spaced-apart sensors at said portable locator at least for sensing said dipole field at a series of spaced-apart reference points along a reference path which reference points are associated one-for-one with a series of spaced-apart measuring locations of the inground device, as the inground device moves along the path, so that each reference point on the reference path is specifically determined by an associated one of the measuring locations; and a processing arrangement for using the set of positional information that is obtained corresponding to each of the spaced-apart reference points, either as being obtained or thereafter, to establish an actual path taken by the inground device and containing the measurement locations.