Establishing positions of locating field detectors and path mapping in underground boring tool applications

Abstract

Specific apparatus and associated methods are described for use in establishing the positions of locating field detectors and for path mapping within a region for the purpose of tracking and/or guiding the movement of an underground boring tool. In one aspect, an improvement is provided forming part of an arrangement for tracking the position and/or guiding the boring tool using an electromagnetic locating signal which is transmitted from the boring tool as the boring tool moves through the ground. At least two detectors are located at fixed positions within the region, each being operable in a transmit mode and in a receive mode such that each one of the detectors in the transmit mode is able to transmit a relative locating signal to the other detector for use in determining the relative position of one detector in relation to the other and such that both detectors receive the electromagnetic locating signal in the receive mode for use in determining the position of the boring tool within the region. Provisions are also described for extending drilling range by using additional detectors by moving a limited number of detectors. In another aspect, a system is provided including at least two above ground detectors for sensing the locating signal. The detectors are located at initial positions in the region. Electromagnetic data is generated by the detectors with the boring tool at multiple positions to generate electromagnetic data which is used to identify the positions of the detectors. A selected flux pathline steering technique is introduced.

What is claimed is: 
     
         1 . An apparatus as part of a system in which a transmitter is moved through the ground in a region for tracking a position of the transmitter as the transmitter emits an electromagnetic locating signal, said apparatus comprising:
 a transceiver detector located at a fixed position within said region for transmitting a relative locating signal in a setup mode and for receiving the electromagnetic locating signal in a tracking mode for use in establishing the position of the transmitter; and   at least one receiver detector at another fixed position within said region for receiving said relative locating signal in said setup mode such that a relative position of the receiver detector can be established in relation to the position of the transceiver detector based on the relative locating signal and for receiving the electromagnetic locating signal in said tracking mode for use in establishing the position of the transmitter.   
     
     
         2 . The apparatus of  claim 1  wherein said transceiver detector includes an antenna array for receiving said electromagnetic locating signal and for transmitting said relative locating signal using said antenna array when the transceiver detector is in said setup mode. 
     
     
         3 . The apparatus of  claim 2  wherein the antenna array of said transceiver detector includes three antennas arranged along three orthogonal axes. 
     
     
         4 . The apparatus of  claim 3  wherein the transceiver detector is configured to transmit the relative locating signal alternately from each one of the three orthogonally arranged antennas for receipt at least by the receiver detector. 
     
     
         5 . The apparatus of  claim 1  wherein said transceiver detector and said receiver detector are configured for receiving said electromagnetic locating signal to produce electromagnetic data in said setup mode and wherein said apparatus includes a processor that is configured for using certain information including the electromagnetic data in conjunction with the relative position established between the transceiver detector and the receiver detector to determine positions of the transmitter, the receiver detector and the transceiver detector within said region. 
     
     
         6 . The apparatus of  claim 5  wherein said transceiver detector and said receiver detector each include a tilt sensor for measuring the tilt angles of the transceiver detector and receiver detector such that the tilt angles form part of said certain information. 
     
     
         7 . The apparatus of  claim 5  wherein said apparatus is configured for receiving said electromagnetic locating signal in a predetermined way by initially using the transceiver and receiver detectors to receive the electromagnetic locating signal with said transmitter at a first position to produce a first subset of said electromagnetic data and then using the transceiver and receiver detectors to receive the electromagnetic locating signal with said transmitter at a second position to produce a second subset of said electromagnetic data and said processor is configured for combining the first and second subsets of electromagnetic data, along with the established relative position between the transceiver and receiver detectors, in determining the positions of the transceiver and receiver detectors in said region. 
     
     
         8 . The apparatus of  claim 5  wherein said system includes a drill rig having an extendable drill string attached to an inground tool which supports said transmitter such that movement of the transmitter is accomplished by moving the inground tool to extend or retract the drill string and the system also includes a drill string measurement apparatus for measuring movement of the inground tool based on retraction and extension of said drill string and wherein said apparatus is configured for receiving said electromagnetic locating signal in said predetermined way by initially using the transceiver and receiver detectors to receive the electromagnetic locating signal with said transmitter at a first position to produce a first subset of said electromagnetic data and then using the transceiver and receiver detectors to receive the electromagnetic locating signal with said transmitter at a second position to produce a second subset of said electromagnetic data, said first and second positions being separated by a measured distance as determined by said drill string measurement apparatus, and, thereafter, said processor is configured for combining the first and second subsets of electromagnetic data, along with the established relative position between the detectors and said certain information, including said measured distance, to determine absolute positions of the transceiver and receiver detectors in said region. 
     
     
         9 . The apparatus of  claim 8  further configured for producing one or more additional subsets of said electromagnetic data at one or more additional positions of said inground tool, said additional subsets of electromagnetic data, thereafter, being used in a way which improves accuracy in determining the absolute positions of the transceiver and receiver detectors in said region.