Rotation-Invariant Geophysical EM Surveying via 3D Vector Analysis
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Solution Overview
Problem
Geophysical EM prospecting methods face challenges in accurately measuring underground conductors due to assumptions about horizontal magnetic field components and sensor attitude instability, leading to errors in surveying.
Innovation Solution
A multiple receiver coil system with a skeletal frame design that maintains coils in orthogonal planes, reducing drag and noise, and uses 3D vector magnitude comparisons between airborne and ground sensors to detect underground conductors independently of tilt angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If assumptions about horizontal magnetic field components are used in AFMAG surveying, then the measurement process is simplified, but measurement precision deteriorates due to errors from sensor attitude instability
Solution Approach 1:
The patent replaces mechanical attitude sensors with a magnetic field vector analysis system. Instead of mechanically measuring and correcting for sensor tilt angles, the system uses mathematical analysis of magnetic field vector components to achieve rotation-invariant measurements, eliminating the mechanical sensing apparatus and its associated errors
Solution Approach 2:
The patent changes the measurement parameters from relying on horizontal magnetic field components (which are attitude-dependent) to using rotation-invariant parameters derived from the full magnetic field vector. This parameter transformation eliminates sensitivity to sensor orientation while maintaining measurement simplicity
2Measurement precision
If attitude sensors are used to correct for sensor tilt, then measurement precision may be improved, but device complexity increases
Solution Approach 1:
The patent eliminates mechanical attitude sensors entirely and replaces them with a computational approach using magnetic field vector analysis. The system achieves attitude compensation through mathematical processing of field measurements rather than through additional mechanical sensing devices
Solution Approach 2:
The patent extracts and removes the attitude sensor component from the measurement system, relying instead on the inherent information contained in the magnetic field vector measurements themselves to achieve rotation-invariant results
3Measurement precision
If multiple receiver coils are used in orthogonal planes, then measurement precision improves through 3D vector magnitude comparisons, but device complexity increases due to additional coils and frame structure
Solution Approach 1:
The patent transitions from two-dimensional horizontal field measurements to three-dimensional vector magnitude measurements by adding receiver coils in orthogonal planes. This dimensional expansion enables rotation-invariant measurements through comparison of 3D vector magnitudes between airborne and ground sensors
Solution Approach 2:
The multiple orthogonal receiver coils serve multiple functions simultaneously: they measure magnetic field components in three dimensions, enable rotation-invariant measurements, and provide redundancy for noise reduction, maximizing the utility of the additional hardware
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 enhances the accuracy of geophysical surveys by reducing errors caused by sensor attitude and ionospheric variations, providing stronger signal-to-noise ratios and simplifying instrumentation by eliminating the need for attitude sensors.
Implementation Method 1
Audio Frequency Magnetic (AFMAG) surveying in which the EM fields resulting from naturally occurring primary signal sources such as lightning discharges are measured
Data Source
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AI summary
A geophysical survey method and system that comprises: measuring along multiple axes at multiple locations within a survey area magnetic field components of a low frequency magnetic field resulting from naturally occurring electromagnetic sources using a first sensor system; measuring along multiple axes magnetic field components of a low frequency magnetic field resulting from naturally occurring electromagnetic sources using a second sensor system; and receiving information about the magnetic field components measured by the first sensor system and the second sensor system and in dependence thereon computing parameters from the received information that are independent of rotation of the first sensor system or the second sensor system about any axis thereof.