Indoor Localization via Magnetic Fingerprint Sequence Matching
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Solution Overview
Problem
Existing indoor localization methods using geomagnetic fields and step counters face challenges in large, spacious settings due to computational complexity and limited convergence in environments with high degrees of freedom, requiring costly infrastructure and time-consuming survey procedures.
Innovation Solution
The proposed solution involves creating a magnetic fingerprint map using geomagnetic field measurements and step counter data, employing modified algorithms like the Smith-Waterman algorithm for sequence matching and conditional random fields to accurately locate mobile devices indoors, with Magil using geomagnetic fields alone and Mapel combining geomagnetic fields with step counter information for improved localization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If recursive Bayesian filters (HMMs, particle filters) are used for geomagnetic localization, then location estimation can be performed, but computational complexity becomes too high for mobile devices
Solution Approach 1:
The patent segments the indoor environment into discrete grid cells and divides the localization problem into matching magnetic field sequences against pre-collected fingerprint data for each cell. This segmentation transforms the complex continuous space problem into discrete, manageable units that can be processed efficiently on mobile devices.
Solution Approach 2:
The patent performs preliminary magnetic field fingerprint collection and processing during an offline survey phase, storing pre-computed magnetic field sequences for each grid cell. During online localization, the mobile device only needs to match its current magnetic field readings against these pre-prepared fingerprints, dramatically reducing real-time computational requirements.
2Reliability
If traditional geomagnetic localization models are used, then they work well for partitioned environments with narrow corridors, but they barely converge for large spacious settings with high degrees of freedom
Solution Approach 1:
The patent develops a universal localization framework that works across diverse indoor environments including narrow corridors, open spaces, and complex layouts. The grid-based magnetic fingerprinting approach with sequence matching provides a unified solution that adapts to different environment types without requiring model adjustments, achieving both reliability and versatility.
Solution Approach 2:
The patent enhances the localization approach by incorporating temporal dimension through magnetic field sequence matching over time, and spatial dimension through grid cell decomposition. This multi-dimensional approach provides sufficient constraints even in large open spaces with high degrees of freedom, enabling reliable convergence across diverse environments.
3Ease of operation
If pervasive infrastructure installations are used for indoor localization, then location services can be provided, but system cost increases significantly
Solution Approach 1:
The patent enables mobile devices to perform self-service localization using only the magnetometer and processor already present in the device. The system utilizes the Earth's magnetic field and local magnetic anomalies as natural fingerprints, eliminating the need for expensive infrastructure installations while maintaining localization service availability.
Solution Approach 2:
The patent replaces physical infrastructure-based localization systems with a field-based approach using magnetometers. Instead of requiring deployed beacons, anchors, or specialized hardware, the system substitutes these mechanical/physical infrastructure elements with measurements of the magnetic field, dramatically reducing system cost while maintaining functionality.
4Measurement precision
If magnetic field fingerprint collection is performed by standing at fixed points, then survey data can be collected, but the survey procedure becomes time-consuming
Solution Approach 1:
The patent transitions from static fixed-point fingerprint collection to dynamic mobile fingerprint collection. Surveyors walk through the environment while continuously collecting magnetic field data, which is then associated with grid cells based on position estimates. This dynamic approach dramatically reduces survey time while maintaining data quality through the use of magnetic field sequences and matching algorithms.
Solution Approach 2:
The patent implements periodic magnetic field sampling during the survey process, collecting measurements at regular time intervals or distance intervals. This periodic collection strategy ensures sufficient data density for accurate fingerprinting while optimizing survey speed, allowing rapid coverage of large areas without sacrificing measurement quality.
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 location accuracy and reduces computational complexity, enabling effective indoor localization in diverse environments without the need for extensive infrastructure, by matching magnetic field changes to fingerprint maps and using step counter data to constrain possible locations.
Implementation Method 1
measuring a geo-magnetic field using a magnetometer of a mobile device
Data Source
AI summary
Various embodiments disclosed herein enable a mobile device to accurately locate where the mobile device is located indoors by measuring geomagnetic fields, and tracing relative changes in the magnetic fields as the mobile device is moved. The relative changes can be compared to a fingerprint signal map, and a trace of a portion of the path can be determined by matching the relative changes in the magnetic fields to relative changes in the fingerprint signal map. A collection of the path portions can then be connected by determining a shortest path that connects each of the path portions. In another embodiment, a step counter can also be used to constrain possible locations, and fuse the geomagnetic field and step counter information for joint indoor localization.