Triaxial Magnetometer Borehole Characterization of Metallic Interference Masses
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Solution Overview
Problem
Current methods for detecting and characterizing metallic interference masses, such as unexploded ordnance, under a ground surface are limited in providing detailed characterization while maintaining cost-effectiveness and accuracy, particularly in distinguishing between hazardous and non-hazardous metal objects.
Innovation Solution
A method combining electromagnetic excitation at the ground surface with chronological evaluation of magnetic reaction signals in three orthogonal spatial axes, using a triaxial magnetometer in boreholes to characterize the shape and orientation of metallic objects, and employing a compensation step to reduce interference, with multiple borehole measurements and varying depths to enhance detection precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromagnetic excitation and chronological evaluation of magnetic reaction signals in three orthogonal spatial axes is used, then characterization precision of metallic interference mass is improved, but device complexity and measurement time increase
Solution Approach 1:
The measurement process is segmented into three separate orthogonal spatial axes (x, y, z), with each axis measured independently by dedicated magnetometer components. This segmentation allows complex three-dimensional characterization to be broken down into manageable one-dimensional measurements along each axis, improving precision while organizing device complexity into modular components.
Solution Approach 2:
The invention transitions from conventional single-axis or planar measurements to three-dimensional spatial characterization by adding measurements in the vertical (depth) dimension alongside horizontal axes. This dimensional expansion enables full volumetric characterization of metallic interference masses, significantly improving detection precision through comprehensive spatial analysis.
2Measurement precision
If multiple borehole measurements at various depths are performed, then detection precision is improved, but loss of time and productivity decrease
Solution Approach 1:
The method performs preliminary compensation measurements at each borehole position before conducting the actual detection measurements. This preliminary action establishes a baseline that accounts for environmental interference and equipment characteristics, allowing subsequent measurements to be more efficient and precise without requiring excessive repetition or correction iterations.
Solution Approach 2:
The measurement process employs periodic action by conducting systematic measurements at multiple discrete depth intervals throughout the borehole. Rather than continuous measurement, the magnetometer is positioned at periodic depth increments, which efficiently captures the vertical variation in magnetic signals while minimizing total measurement time and maintaining high detection precision.
3Measurement precision
If triaxial magnetometer with compensation step is used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The compensation step acts as an intermediary process that mediates between the raw magnetometer signals and the final detection results. By introducing this intermediate compensation measurement that accounts for environmental magnetic interference and equipment baseline characteristics, the system achieves higher measurement precision without requiring fundamentally more complex detection hardware.
Solution Approach 2:
The system performs self-characterization by using the compensation measurements taken at each borehole position to automatically establish its own baseline and correction factors. This self-service approach allows the measurement system to adapt to local environmental conditions and equipment variations without requiring external calibration or complex pre-programming, improving precision while keeping the device architecture relatively simple.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for a more detailed and accurate characterization of metallic interference masses, reducing interference and improving detection capabilities, enabling effective differentiation between unexploded ordnance and non-hazardous metal objects with reduced expenses.
Implementation Method 1
electromagnetic pulses are transmitted into the ground by means of an excitation coil
Implementation Method 2
A receiver unit then measures an electromagnetic pulse response that is emitted due to eddy currents in metallic objects
Implementation Method 3
In this connection, measuring a response signal as a magnetic field is an excellent approach because it yields a very sensitive detection specifically of a decay behavior of the response signal
Data Source
Figure 1~4
Figure 2a~2c
AI summary
The present invention relates to a method for characterizing a metallic interference mass S that lies concealed under a ground surface BO, in particular for detecting unexploded ordnance, where at the ground surface BO, a bore hole B is sunk close to a position P of the metallic interference mass S, at least down to a depth T that corresponds to the position of the metallic interference mass S, and electromagnetic pulses are transmitted via an excitation loop Tx into the ground around the bore hole B and a pulse response A is measured in a receiver unit Rx, with the receiver unit Rx being lowered into the bore hole B. In order to create a method to further improve the detection possibilities with the goal of a more detailed characterization of a metallic interference mass for a reduced expense, the invention proposes that a pulse response A of the interference mass S with a chronological progression be detected and evaluated in the receiver unit Rx by means of a magnetic sensor or magnetometer M, in all three spatial axes x, y, z in the bore hole B.