Abstract
Recent successful flight tests have demonstrated scalar magnetic anomaly navigation to be a viable GPS-alternative navigation system. These flight tests matched magnetic field measurements to maps of the Earth's crustal magnetic field in order to navigate. Scalar magnetic navigation uses only the magnetic field intensity, not direction, in order to navigate. While it appears obvious to extend aerial magnetic navigation to use the full vector field, in practice there are substantial obstacles to doing so. This article explores the key challenges of magnetic vector navigation including current sensor limitations, lack of high frequency magnetic vector maps of the Earth's crust, and proper integration of the magnetic data with an inertial navigation system. In overcoming these challenges several key benefits of magnetic vector navigation over scalar magnetic navigation become apparent, including modestly improved navigation accuracy and greatly improved platform attitude.
Highlights
Magnetic anomaly navigation is a flight-test proven navigation technique to address the vulnerabilities of GPS [1]
Multiple flight tests have demonstrated the usefulness of scalar magnetic measurements for navigation [2]
Two primary magnetic sources caused by the Earth are the Earth’s core magnetic field (Bcore) and the Earth’s crustal magnetic field (Bcrustal)
Summary
If a vehicle with a 3-axis magnetometer goes over a bump in the road which changes the vehicle attitude by a few degrees, a large magnetic signal of hundreds of nanotesla may appear in the body-frame measurements This is not a true magnetic field variation, but it is a repeatable signal that can be mapped and used to navigate. Considering that scalar data has excellent world-wide coverage and no attitude dependencies, it can appear that magnetic vector navigation is not practical to pursue This is mainly due to two issues which can each be overcome: the need for high resolution maps, and extremely precise attitude requirements. Methods to overcome these two primary obstacles to vector magnetic navigation are provided in this article.
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