Magnetic Anomaly Navigation Accuracy with Respect to Map Quality and Altitude

Abstract

Accurate positioning without the use of GPS is a difficult engineering problem. Many alternative technologies exist, each with their own limitations and benefits. Often, these limitations restrict where and when the alternative systems may be used. Navigating with the Earth’s magnetic anomaly field shows potential to overcome these common limitations by being available at all times, world-wide. High accuracy regional navigation has been successfully demonstrated using the Earth’s magnetic anomaly field. Map availability has been identified as a key concern in practical implementation of magnetic anomaly navigation systems. While a large patchwork of high accuracy magnetic anomaly maps exist, current large scale compilation maps are less accurate and generally lower resolution. The North American Magnetic Anomaly Database (NAMAD) is a continent-sized magnetic anomaly map. In this paper, we demonstrated the obtainable accuracies when navigating with the NAMAD using real flight test data. The navigation accuracy over a 5 hour 1500km flight was approximately 3.2 km DRMS. Through simulation and a Cramer-Rao Lower Bound (CRLB) analysis, we show the majority of this positioning error is related to map accuracy. Through simulation, we predict DRMS errors of approximately 160 meters for the same flight using an improved magnetic anomaly map. Finally, we extend our CRLB analysis to predict navigation accuracies over various altitudes.