Method for determining the depth of an in-ground boring tool

• US 5,990,682 A
• Filed: 04/13/1998
• Issued: 11/23/1999
• Est. Priority Date: 03/01/1991
• Status: Expired due to Fees

• Current Assignee: Merlin Technologies Incorporated
• Original Assignee: Digital Control Incorporated
• Inventors: Mercer, John E.
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US09/059,246
• Time in Patent Office: 589 Days
• Field of Search: 324/326, 324/327, 324/328, 324/329, 324/225, 324/226, 324/262, 324/207.12, 324/207.25, 324/207.16, 702/150, 702/152, 702/153, 175/40, 175/45
• US Class Current: 324/326
• CPC Class Codes: E21B 47/0228 using electromagnetic energy or detectors therefor
• CPC Class Codes: E21B 47/0232 at least one of the energy sources or one of the detectors being located on or above the ground surface
• CPC Class Codes: E21B 47/024 of devices in the borehole determining slope or direction of the borehole E21B47/022
• CPC Class Codes: G01C 9/06 Electric or photoelectric indication or reading means
• CPC Class Codes: G01C 9/20 the indication being based on the inclination of the surface of a liquid relative to its container
• CPC Class Codes: G01V 3/165 operating with magnetic or electric fields produced or modified by the object or by the detecting device with electromagnetic waves G01V3/17

Abstract

The present invention provides a locator/monitor capable of locating a boring tool and monitoring the progress of the tool for control purposes. The locator/monitor may be used in expedited locating methodology and straightforward calibration techniques of the present invention. A durable and cost effective pitch sensor is also provided by the present invention. In addition, the present invention provides a slotted transmitter housing formed of an electrically conductive material, where the magnetic field generated by the transmitter is capable of penetrating to the surface.

Claims

1. In an overall method of determining the depth of an in-ground boring tool containing a magnetic field transmitter by (i) causing the transmitter to produce a magnetic field signal when the boring tool is beneath the ground, (ii) using a calibrated locator above ground to sense and thereby measure the field strength of the magnetic field signal at a number of different points, and (iii) from the measurements, determining the depth of the boring tool, a method of calibrating said locator, comprising the steps of:

(a) establishing an above-ground reference surface;

(b) using the locator, sensing and thereby measuring the magnetic field signal strengths at first and second distances from the reference surface so as to obtain corresponding first and second measurements, respectively, and storing said first and second measurements;

(c) measuring and storing said first and second distances from the reference surface; and

(d) calculating the proportionality constant of the magnetic field signal produced by said transmitter from the stored first and second measurements and from the stored first and second distances.

2. In an overall system for determining the depth of an in-ground boring tool containing a magnetic field transmitter by (i) causing the transmitter to produce a magnetic field signal when the boring tool is beneath the ground, (ii) using a calibrated locator above ground to sense and thereby measure the field strength of the magnetic field signal at a number of different points, and (iii) from the measurements, determining the depth of the boring tool, an arrangement for calibrating said locator, comprising the steps of:

(a) means for sensing and thereby measuring the magnetic field signal strengths at first and second distances from a reference surface so as to obtain corresponding first and second measurements, respectively, and means for storing said first and second measurements;

(c) means for measuring and storing said first and second distances from the reference surface; and

(d) means for calculating the proportionality constant of the magnetic field signal produced by said transmitter from the stored first and second measurements and from the stored first and second distances.