Inexpensive three‐axis magnetometers can sense not just heading, but also variations in Earth's magnetic field. Combined with a magnetic field map, this information can be used for positioning. Pairing the three‐axis magnetometer measurements with position information from a ground vehicle creates a magnetic field map containing the variation and localized perturbations in Earth's magnetic field as a function of position. A magnetometer and the magnetic field map can then be used for navigation. This paper describes how magnetometer measurements can be used to calculate a position update using three different likelihood functions, and it also demonstrates direct incorporation of magnetic field measurements into a map‐matching particle filter. These algorithms were tested in three different vehicles under a variety of road conditions and demonstrated meter‐level positioning when local magnetic field features are available. Overall the information is sufficient for road level navigation when used as the sole source of navigation information. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
The 746th Test Squadron at Holloman AFB has developed and utilized the Central Inertial Guidance Test Facility (CIGTF) High Accuracy Post-processing Reference System (CHAPS). CHAPS is a multi-sensor navigation reference system used to evaluate position, velocity, and attitude performance of Global Positioning System (GPS), Inertial Navigation System (INS), and Embedded GPS/INS (EGI) navigation systems on large vehicles and aircraft. Reference data is processed post-test with accuracy ranges from a meter to sub-meter depending on the reference configuration and test environment (profile, trajectory dynamics, GPS jamming, etc.). The GPS Aided Inertial Navigation Reference (GAINR) system developed by the Air Force Flight Test Center (Edwards AFB) offered other utilization capabilities (test beds and post-processing time). The basic sensor assembly is an EGI navigation system. The data are post-processed with Multisensor Optimal Smoothing Estimation Software (MOSES). Incorporating CHAPS and GAINR capabilities generates a reference system with enhanced accuracy (sub-meter) in a dynamic GPS non-jamming/jamming environment. This paper will present the enhanced reference system combination of CHAPS/GAINR capabilities, characterization process and development methodology.
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