Patent ID: 8381836

Claim:
In a system including a boring tool that is moved by a drill string using a drill rig that selectively extends the drill string to the boring tool to form an underground bore such that the drill string is characterized by a drill string length which is determinable, a homing apparatus comprising: a transmitter, forming part of the boring tool, for transmitting a time varying dipole field as a homing field; a pitch sensor located in the boring tool for detecting a pitch orientation of the boring tool; a homing receiver that is positionable at least proximate to a target location for detecting the homing field to produce a set of flux measurements; a processing arrangement that is configured for using the detected pitch orientation and the set of flux measurements in conjunction with a determined length of the drill string to determine a vertical homing command for use in controlling depth in directing the boring tool to said target location such that the vertical homing command is generated with a particular accuracy at a given range between the transmitter and the homing receiver and which would otherwise be generated with said particular accuracy for a standard range, that is different from the given range, without using the determined length of the drill string; and a display for indicating said vertical homing command to a user.