Magnetic Anomaly Map Conversion for Stable Altitude Navigation
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Solution Overview
Problem
Existing methods for lifting and lowering magnetic anomalies in magnetic navigation systems, such as the Fast-Fourier-Transform (FFT) method, are inaccurate and unstable, introducing constant biases and errors, particularly when converting between latitude-longitude-altitude (LLA) and Earth-Centered Earth-Fixed (ECEF) coordinates.
Innovation Solution
The use of the Strakhov integration method in conjunction with Earth-Centered Earth-Fixed (ECEF) coordinates to accurately lift and lower magnetic anomalies, employing a two-step process to convert 2D maps from LLA to ECEF coordinates and perform Strakhov iterations to compute magnetic anomalies, allowing for accurate navigation at various altitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the FFT method is applied to lift magnetic anomalies from anomaly maps, then computational efficiency is improved, but measurement precision deteriorates due to introduction of constant bias and errors
Solution Approach 1:
The patent introduces an intermediary coordinate transformation step that converts magnetic anomaly data from LLA coordinates to a local tangent plane coordinate system before applying FFT. This intermediary transformation resolves the coordinate system incompatibility that causes FFT to introduce bias, thereby maintaining both computational efficiency and measurement precision.
Solution Approach 2:
The patent changes the coordinate system parameters from global LLA coordinates to local tangent plane coordinates, and adjusts the FFT application parameters to match the transformed coordinate system. This parameter change eliminates the fundamental incompatibility between FFT assumptions and LLA coordinate geometry, resolving the precision issue while preserving computational efficiency.
2Productivity
If the FFT method is used to lower magnetic anomalies to altitudes below the reference map altitude, then computational speed is maintained, but reliability deteriorates due to instability
Solution Approach 1:
The patent applies preliminary coordinate transformation and bias correction operations before the FFT lowering process to counteract the instability that would otherwise occur. By preparing the data in advance with appropriate transformations, the method prevents the reliability issues that arise during the lowering operation while maintaining computational speed.
3Ease of operation
If magnetic anomaly maps in LLA coordinates are processed directly by FFT, then ease of operation is maintained, but manufacturing precision deteriorates due to coordinate system incompatibility
Solution Approach 1:
The patent performs preliminary coordinate transformation from LLA to tangent plane coordinates, and pre-computes correction factors, before applying FFT to the magnetic anomaly data. This preliminary preparation maintains ease of operation by automating the transformation process while ensuring manufacturing precision through proper coordinate system alignment.
Data Source
AI summary
A system and method for magnetic navigation are provided. The system comprises a navigation system for a vehicle, at least one processor operatively coupled with the navigation system, and a magnetic navigation module operatively coupled with the processor. The magnetic navigation module including instructions, executable by the processor, to perform a method comprising selecting latitude, longitude, and altitude ranges for the vehicle that is expected to travel in a region of interest; obtaining one or more magnetic anomaly maps for the region of interest; choosing a base Earth-centered, Earth-fixed (ECEF) plane and coordinates for the one or more magnetic anomaly maps; constructing an integration mesh on the base ECEF plane; and performing a Strakhov iteration process on the integration mesh to compute values of magnetic anomalies on a base source. The method then computes an estimated magnetic anomaly at a given point in space using alternative computation approaches.