Magnetic Anomaly Positioning Using Sequential Measurements
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Solution Overview
Problem
GNSS signals are susceptible to jamming and spoofing, leading to inaccurate geographic position determination using single magnetic anomaly measurements, as multiple locations may have similar magnetic field strengths, resulting in erroneous geographic positions.
Innovation Solution
Utilize a series of magnetic anomaly measurements to generate a set of geographic locations within a threshold range, determine vector distances, and refine these locations to a single accurate position using inertial navigation data, compensating for magnetic effects from the body, space weather, and Earth's core field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single magnetic anomaly measurement is used to determine geographic location, then the determination process is simple and fast, but the accuracy is poor because multiple locations may have similar magnetic field strengths
Solution Approach 1:
The patent segments the geographic area into a grid of cells, each with pre-calculated average magnetic field strengths for the three magnetic components. This segmentation allows the system to compare measurements against multiple discrete location candidates rather than treating the area as continuous, improving location accuracy while managing computational complexity.
Solution Approach 2:
The patent transitions from using a single magnetic measurement value to using three-dimensional magnetic field component data (X, Y, Z components). By incorporating multiple dimensional measurements and comparing them against pre-calculated three-component averages for each grid cell, the system resolves ambiguities that would exist with single-value comparisons.
2Measurement precision
If multiple magnetic measurements are taken to resolve location ambiguity, then location accuracy improves, but the time required for position determination increases
Solution Approach 1:
The patent performs preliminary calculations during an offline mapping phase, pre-computing average magnetic field strengths for each grid cell and storing them in a lookup table. During actual navigation, the system only needs to compare current measurements against these pre-computed values, dramatically reducing real-time computational requirements and enabling faster position determination.
Solution Approach 2:
The system uses feedback from sequential measurements to refine location estimates. By comparing the first measurement against multiple candidate locations and then using a second measurement to eliminate incorrect candidates, the system iteratively narrows down the possible locations, achieving high accuracy through adaptive feedback rather than requiring all measurements simultaneously.
3Reliability
If magnetic anomaly measurements are used as an alternative to GNSS, then position determination is possible without satellite signals, but the reliability is reduced due to ambiguity in magnetic field strength matching
Solution Approach 1:
The patent merges multiple independent magnetic component measurements (X, Y, Z components) into a comprehensive location determination process. By combining information from all three magnetic components and comparing them against corresponding pre-calculated averages for each grid cell, the system creates a more robust and reliable location estimate that overcomes the limitations of using any single measurement.
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
Enhances the accuracy of geographic position determination by reducing ambiguity in magnetic anomaly maps, providing a more precise geographic location for navigation filters.
Implementation Method 1
magnetic anomaly measurements... The magnetic anomaly measurement at each time instance is used to aid position determination
Data Source
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AI summary
Techniques are provided for generating more accurate aiding data from magnetic anomaly measurements to aid in determining geographic position of a body. The following data is acquired: a series of more than one magnetic anomaly measurement (e.g., made with a magnetometer), a corresponding time of each magnetic anomaly measurement, and a vector distance between each successive magnetic anomaly measurement. With a single magnetic anomaly measurement, more than one geographic location on the magnetic anomaly map may be identified. As the number of magnetic anomaly measurements increases, a number of geographic locations diminishes eventually to a single geographic location on a magnetic anomaly map. Once determined, the single geographic location and a time is transmitted to a navigation filter.