Mapping tool for tracking and/or guiding an underground boring tool

A method of tracking the position and certain orientation parameters of a boring tool in the ground as the latter moves along a path which lies within a particular coordinate system, said method comprising the steps of:

• (a) providing the boring tool with means for transmitting an electromagnetic field;
• (b) providing at least two detectors, each having an electromagnetic field receiving antenna assembly including first, second and third antennas which are orthogonal with respect to one another, locating each detector provided at a fixed position and at a particular orientation within said coordinate system but not necessarily along the intended path of movement of said boring tool, and determining the position and particular orientation within said coordinate system of the antenna associated with each detector provided;
• (c) at least periodically transmitting said electromagnetic field from said boring tool when the boring tool is at certain positions on said path;
• (d) when the boring tool is at one point on said path, establishing its position and said certain orientation parameters of the boring tool within the coordinate system;
• (e) moving said boring tool along said path which includes said one point and at least a subsequent second point;
• (f) when the boring tool moves a distance along said path from said one point to said second point, measuring at least one component of the intensity of said electromagnetic field using said detectors;
• (g) determining, at least to an approximation, the position and orientation of the boring tool at said second point within the coordinate system using as a first input the electromagnetic field intensity measurement or measurements taken by said detectors when the boring tool is at said second point;
• and
• (h) providing a mapping tool having means for transmitting an electromagnetic field and a tilt sensing mechanism, said mapping tool being used to determine the positions and orientations of all of said first, second and third antennas within said coordinate system.