Precise location of buried metallic pipes and cables in the presence of signal distortion
First Claim
1. A method for precise location of underground cables and pipes, comprising:
- measuring a set of complex electromagnetic field strengths at a plurality of positions along a path that crosses a target line;
modeling an expected complex field strength at each of the plurality of positions with the target line and a hypothesized number of bleedover cables to form a set of hypothesized values corresponding to a set of individual models for the target line for each of the hypothesized number of bleedover cables;
determining which of the set of individual models is a best model; and
determining parameters related to the target line from the best model.
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Abstract
A new approach for locating an underground line described herein remains accurate in the face of bleedover by including both amplitude and phase from at least two magnetic field strength sensors in the measurement set. A numerical optimization step is introduced to deduce the positions and currents of each of several cables, of which one is the targeted cable and the others are termed bleedover cables. Furthermore, some embodiments of the method accounts for practical problems that exist in the field that relate to reliable estimation of cable positions, like the phase transfer function between transmitter and receiver, the estimation of confidence bounds for each estimate, and the rejection of false positive locates due to the presence of noise and interference.
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Citations
44 Claims
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1. A method for precise location of underground cables and pipes, comprising:
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measuring a set of complex electromagnetic field strengths at a plurality of positions along a path that crosses a target line;
modeling an expected complex field strength at each of the plurality of positions with the target line and a hypothesized number of bleedover cables to form a set of hypothesized values corresponding to a set of individual models for the target line for each of the hypothesized number of bleedover cables;
determining which of the set of individual models is a best model; and
determining parameters related to the target line from the best model. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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37. A line locator, comprising:
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a plurality of coil detectors, each of the plurality of coil detectors oriented to measure a component of a magnetic field;
circuitry coupled to receive signals from the plurality of coil detectors and provide quadrature signals indicating a complex magnetic field strength;
a position locator for indicating a position of the line locator;
a processor coupled to receive the complex magnetic field strength and the position and calculate values related to a target line; and
a display coupled to the processor, the display indicating to a user the values related to the target line, wherein the processor includes software for performing the following;
modeling an expected complex field strength corresponding to complex field strengths measured at the plurality of coil detectors at each of a plurality of positions determined by the position locator with the target line and a hypothesized number of bleedover cables to form a set of hypothesized values corresponding to a set of individual models for the target line for each of the hypothesized number of bleedover cables;
determining which of the set of individual models is a best model; and
determining parameters related to the target line from the best model. - View Dependent Claims (38, 39, 40, 41, 42, 43, 44)
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Specification